Fixing replacement of an existing many-to-many relation. Fixes #537.
Fixing replacement of an existing many-to-many relation. Fixes #537.

fredjean/mongoid,bdmac/mongoid,KoanHealth/mongoid,byroot/mongoid,aileron/mongoid,kevinmarvin/mongoid,cmpolis/mongoid,captain-lucas/mongoid,incorvia/mongoid,hubertlepicki/mongoid,dustinwatson/mongoid,subhashb/mongoid,sikachu/mongoid,toppan-forms/mongoid,freerange/mongoid,jeffreyiacono/mongoid,joshsoftware/mongoid,jim/mongoid,spiegela/mongoid,joshleitzel/mongoid,tvon/mongoid,hashrocketeer/mongoid,flyerhzm/mongoid,notxarb/mongoid,greggroth/mongoid,HRNewMedia/mongoid,jbrien/mongoid,Shop2market/mongoid,rebelhold/mongoid,tengine/mongoid,evansagge/mongoid,tetsuo692/mongoid,potatosalad/mongoid,asantamar/mongoid,narutosanjiv/mongoid,dakatsuka/mongoid,tolsen/mongoid,demarque/mongoid,JonRowe/mongoid,alexrothenberg/mongoid,mongodb/mongoid,spiegela/mongoid,xinuc/mongoid,arunagw/mongoid,tombruijn/mongoid,xentek/mongoid,bencrouse/mongoid,leedo/mongoid,teaforthecat/mongoid,ealdent/mongoid,mikerobe/mongoid,Speakol/mongoid,crowdtap/mongoid,aileron/mongoid,zBMNForks/mongoid,malditogeek/mongoid,Sharevari-Inc/mongoid,ches/mongoid,hfwang/mongoid,razum2um/mongoid,matsimitsu/mongoid,cmpolis/mongoid,sepastian/mongoid,asantamar/mongoid,akirasosa/mongoid,dcu/mongoid,rafaelgaspar/mongoid,praecipula/mongoid,Subskii/mongoid,robinst/mongoid,cncolder/mongoid,gicappa/mongoid,yuuna/mongoid,narutosanjiv/mongoid,hookercookerman/mongoid,drobune/mongoid,eddanger/mongoid,cavneb/mongoid,balauru/mongoid,chetan/mongoid,Welovroi/mongoid,abezzub/mongoid,evansagge/mongoid,brettgoulder/mongoid-1,hashrocketeer/mongoid,nviennot/mongoid,amw/mongoid,cleishm/mongoid,arnkorty/mongoid,77Agency/mongoid,mattconnolly/mongoid,derekharmel/mongoid,jakcharlton/mongoid,skyeagle/mongoid,kslazarev/mongoid,dferdian/mongoid,nfo/mongoid,derickbailey/mongoid,slbug/mongoid,itbakery/mongoid,X0nic/mongoid,grossws/mongoid,jtescher/mongoid,aleksclark/mongoid,florent/mongoid,akm/mongoid,iamnader/mongoid-2,akreiling/mongoid,paulrosania/mongoid,sserdyuk/mongoid,derickbailey/mongoid,zanker/mongoid,getaroom/mongoid,glebtv/mongoid,jiren/mongoid,leedo/mongoid,maxd/mongoid,sideci-sample/sideci-sample-mongoid,niedhui/mongoid,skippy/mongoid,rinmu/mongoid,mathieuravaux/mongoid,gilles/mongoid,hxx/mongoid,franc/mongoid,razum2um/mongoid,JonRowe/mongoid,mgartner/mongoid,stellard/mongoid,adyard/mongoid,sserdyuk/mongoid,franc/mongoid,joneslee85/mongoid,nusco/mongoid,mitio/mongoid,apptentive-engineering/mongoid,amw/mongoid,aj0strow/mongoid,itbakery/mongoid,incorvia/mongoid,mgartner/mongoid,uranazo/mongoid,pkieltyka/mongoid,quipper/mongoid,msaffitz/mongoid,ErisExchange/mongoid,matbox/mongoid,drfeelngood/mongoid,Codas/mongoid,atomical/mongoid,stnguyen/mongoid,matbox/mongoid,joshsoftware/mongoid,sukeerthiadiga/mongoid,balauru/mongoid,hadees/mongoid,abezzub/mongoid,jakcharlton/mongoid,britto/mongoid,4pcbr/mongoid,mongoid/mongoid,canavese/mongoid,stnguyen/mongoid,caiofilipini/mongoid,hadees/mongoid,kay-kim/mongoid,herimedia/mongoid,aagrawal2001/mongoid,mschulkind/mongoid,manikandan-kandasamy/mongoid,tricknotes/mongoid,dnd/mongoid,fortnightlabs/mongoid,dannguyen/mongoid,voldy/mongoid,anuprit/mongoid,ealdent/mongoid,justinko/mongoid,bjori/mongoid,asaaki/mongoid,javmorin/mongoid,jim/mongoid,MadRabbit/mongoid,iGoDigital-LLC/mongoid,mongodb/mongoid,env0der/mongoid,nullstyle/mongoid,adyard/mongoid,slbug/mongoid,gullitmiranda/mongoid,nfo/mongoid,malditogeek/mongoid,janroesner/mongoid,PerfectMemory/mongoid,irakli-janiashvili/mongoid,hfwang/mongoid,wuboy0307/mongoid,cpuguy83/mongoid,FestivalBobcats/mongoid,karmakaze/mongoid,elia/mongoid,dferdian/mongoid,lowang/mongoid,rmm5t/mongoid,sivagollapalli/mongoid,uniiverse/mongoid,moretea/mongoid,aleksclark/mongoid,trmmy/mongoid,alexandru-calinoiu/mongoid,blt04/mongoid,colinyoung/mongoid,greggroth/mongoid,akirasosa/mongoid,manuelmorales/mongoid,etomic/mongoid,lucasas/mongoid,mulder/mongoid,herimedia/mongoid,absperf/mongoid,jetheredge/mongoid,stevebartholomew/mongoid,CIRCUITLLC/mongoid,jtescher/mongoid,tagliala/mongoid,estolfo/mongoid,imomoisoft/mongoid,chriseppstein/mongoid,simi/mongoid,luxerama/mongoid,afeld/mongoid,niedhui/mongoid,tzar/mongoid,fbernier/mongoid,abscondment/mongoid,canvas-drw/mongoid,jstrocel/mongoid,zaithottakath/mongoid,Spaceghost/mongoid,kay-kim/mongoid,yuuna/mongoid,envylabs/mongoid,socialreferral/mongoid,4pcbr/mongoid,tanordheim/mongoid,potatosalad/mongoid,marcweil/mongoid,X0nic/mongoid,zanker/mongoid,Azzurrio/mongoid,lawrencecurtis/mongoid,skippy/mongoid,grossws/mongoid,Exoth/mongoid,asaaki/mongoid,mitijain123/mongoid,korishev/mongoid,brynary/mongoid,genexp/mongoid,shotoso/mongoid,kayakyakr/mongoid,afeld/mongoid,likealittle/mongoid,elia/mongoid,brettgoulder/mongoid-1,travis-repos/mongoid,kentaroi/mongoid,irakli-janiashvili/mongoid,evendis/mongoid,aj0strow/mongoid,eddanger/mongoid,evendis/mongoid,jasl/mongoid,alexrothenberg/mongoid,kuadrosx/mongoid,rosylilly/mongoid,zaithottakath/mongoid,Zhomart/mongoid,tvon/mongoid,Houdini/mongoid,joelcogen/mongoid,zBMNForks/mongoid,dcu/mongoid,drobune/mongoid,akreiling/mongoid,socialreferral/mongoid,christiannelson/mongoid,haihappen/mongoid,kevinmarvin/mongoid,sivagollapalli/mongoid,rpocklin/mongoid,leozhang37/mongoid,jonasschneider/mongoid,skiz/mongoid,Numerico/mongoid,johnnyshields/mongoid,dsachitano/mongoid,alex-klepa/mongoid,dlt/mongoid,stellard/mongoid,hookercookerman/mongoid,tagliala/mongoid,manikandan-kandasamy/mongoid,rymai/mongoid,SumeruSoftware/mongoid,kryzhovnik/mongoid,dbkbali/mongoid,christiannelson/mongoid,derekharmel/mongoid,MSNexploder/mongoid,sukeerthiadiga/mongoid,Winslett/mongoid,bobbytables/mongoid,aagrawal2001/mongoid,sevos/mongoid,skiz/mongoid,lucasas/mongoid,cavneb/mongoid,robwil/mongoid,eljojo/mongoid,jbrien/mongoid,DanielVartanov/mongoid,ginty/mongoid,chriseppstein/mongoid,msaffitz/mongoid,johnny-miyake/mongoid,Speakol/mongoid,haihappen/mongoid,mehowte/mongoid,jeyb/mongoid,mongoid/mongoid,tombruijn/mongoid,astjohn/mongoid,stevebartholomew/mongoid,drfeelngood/mongoid,nullstyle/mongoid,mhs/mongoid,jeffreyiacono/mongoid,HeeL/mongoid-1,timgluz/mongoid,nickhoffman/mongoid,tanordheim/mongoid,akm/mongoid,wuboy0307/mongoid,jordoh/mongoid,apptentive-engineering/mongoid,zenjoy/mongoid,MSNexploder/mongoid,rafaelfranca/mongoid,lackac/mongoid,xinuc/mongoid,trmmy/mongoid,fortnightlabs/mongoid,praecipula/mongoid,colinyoung/mongoid,outoftime/mongoid,sikachu/mongoid,tetsuo692/mongoid,LastStar/mongoid,mschulkind/mongoid,zenjoy/mongoid,korishev/mongoid,Spaceghost/mongoid,jetthoughts/mongoid,DanielVartanov/mongoid,Tickaroo/mongoid2,rosylilly/mongoid,arnkorty/mongoid,pkieltyka/mongoid,notxarb/mongoid,gilles/mongoid,arunagw/mongoid,ono/mongoid,matadon/mongoid,luxerama/mongoid,mikerobe/mongoid,dlt/mongoid,crealytics/mongoid,dannguyen/mongoid,joneslee85/mongoid,manuelmorales/mongoid,ganlron/mongoid,codedogfish/mongoid,gregmolnar/mongoid,camallen/mongoid,mzsanford/mongoid,demarque/mongoid,koraktor/mongoid,uranazo/mongoid,neerfri/mongoid,mulder/mongoid,wyattisimo/mongoid,fujimura/mongoid,tricknotes/mongoid,abscondment/mongoid,brynary/mongoid,EqualMedia/mongoid,sideci-sample/sideci-sample-mongoid,jpfuentes2/mongoid,jseibert/mongoid,blackxored/mongoid,iGoDigital-LLC/mongoid,kslazarev/mongoid,mathieuravaux/mongoid,mongodb/mongoid,charliehq/mongoid,shingara/mongoid,outoftime/mongoid,dustinwatson/mongoid,lackac/mongoid,karmakaze/mongoid,dblock/mongoid,nusco/mongoid,jonhyman/mongoid,kostyantyn/mongoid,parov/mongoid,kuruma-gs/mongoid,estolfo/mongoid,neerfri/mongoid,LastStar/mongoid,77Agency/mongoid,canavese/mongoid,gregory-m/mongoid,bigbenli/mongoid,kuruma-gs/mongoid,priyaaank/mongoid,jordelver/mongoid,kcdragon/mongoid,lowang/mongoid,flada-auxv/mongoid,Subskii/mongoid,PerfectMemory/mongoid,capnregex/mongoid,iboard/mongoid-1,railsjedi/mongoid,cao7113/mongoid,justinko/mongoid,blackxored/mongoid,leemhenson/mongoid,krasnoukhov/mongoid,ryanong/mongoid,codedmart/mongoid,Sharevari-Inc/mongoid,schnittchen/mongoid,gicappa/mongoid,andreychernih/mongoid,kostyantyn/mongoid,rogerz42892/mongoid,Numerico/mongoid,rogerz42892/mongoid,codedmart/mongoid,ches/mongoid,rafaelgaspar/mongoid,cpuguy83/mongoid,mitijain123/mongoid,mysociety/mongoid,travis-repos/mongoid,timgluz/mongoid,tzar/mongoid,subhashb/mongoid,500px/mongoid,jordoh/mongoid,britto/mongoid,goshakkk/mongoid,ElvinEfendi/mongoid,joshleitzel/mongoid,kryzhovnik/mongoid,loginx/mongoid,genexp/mongoid,nextmat/mongoid,theirishpenguin/mongoid,corpgovrisk/mongoid,EqualMedia/mongoid,canvas-drw/mongoid,albus522/mongoid,FestivalBobcats/mongoid,jasonsydes/mongoid,sporkd/mongoid,hubertlepicki/mongoid,nagachika/mongoid,Flameeyes/mongoid,fredjean/mongoid,jpfuentes2/mongoid,kentaroi/mongoid,hxx/mongoid,idesaku/mongoid,moretea/mongoid,bearded/mongoid,cmartyn/mongoid,CIRCUITLLC/mongoid,cgriego/mongoid,cncolder/mongoid,cao7113/mongoid,SumeruSoftware/mongoid,kuadrosx/mongoid,quipper/mongoid,robotmay/mongoid,johnny-miyake/mongoid,kayakyakr/mongoid,ahoward/mongoid,anuprit/mongoid,uniiverse/mongoid,romanbsd/mongoid,florent/mongoid,crowdtap/mongoid,chetan/mongoid,parov/mongoid,paulrosania/mongoid,fbernier/mongoid,robwil/mongoid,rafaelfranca/mongoid,sepastian/mongoid,ebeigarts/mongoid,KoanHealth/mongoid,joelcogen/mongoid,nagachika/mongoid,dbkbali/mongoid,bdmac/mongoid,flada-auxv/mongoid,gregory-m/mongoid,infiverve/mongoid,Welovroi/mongoid,gullitmiranda/mongoid,rinmu/mongoid,mehowte/mongoid,ganlron/mongoid,charliehq/mongoid,bobbytables/mongoid,shingara/mongoid,maxd/mongoid,sevos/mongoid,Exoth/mongoid,jamesalmond/mongoid,hbakhtiyor/mongoid,mattconnolly/mongoid,ErisExchange/mongoid,cleishm/mongoid,janroesner/mongoid,wyattisimo/mongoid,glebtv/mongoid,cjab/mongoid,500px/mongoid,gregmolnar/mongoid,jordelver/mongoid,nviennot/mongoid,mash-ltd/mongoid,HeeL/mongoid-1,nickhoffman/mongoid,DouweM/mongoid,matsimitsu/mongoid,semaperepelitsa/mongoid,shotoso/mongoid,kcdragon/mongoid,cmartyn/mongoid,imomoisoft/mongoid,krasnoukhov/mongoid,icambron/mongoid,snapfish-soma/mongoid,marcweil/mongoid,Zhomart/mongoid,rmm5t/mongoid,johnnyshields/mongoid,piotrj/mongoid,toppan-forms/mongoid,jeyb/mongoid,dnd/mongoid,flyerhzm/mongoid,ebeigarts/mongoid,mgolovnia/mongoid,eljojo/mongoid,ElvinEfendi/mongoid,teaforthecat/mongoid,Codas/mongoid,bigbenli/mongoid,bencrouse/mongoid,flexoid/mongoid,rubrikkfabrikken/mongoid,goshakkk/mongoid,dsachitano/mongoid,camallen/mongoid,sujal/mongoid,jseibert/mongoid,jasl/mongoid,Winslett/mongoid,andreychernih/mongoid,jonhyman/mongoid,sporkd/mongoid,bearded/mongoid,bjori/mongoid,ahoward/mongoid,codedogfish/mongoid,railsjedi/mongoid,infiverve/mongoid,javmorin/mongoid,rubrikkfabrikken/mongoid,mysociety/mongoid,simi/mongoid,freerange/mongoid,Empact/mongoid,etomic/mongoid,Azzurrio/mongoid,jmaicher/mongoid,voldy/mongoid,Aupajo/mongoid-1,corpgovrisk/mongoid,nextmat/mongoid,envylabs/mongoid,lawrencecurtis/mongoid,rpocklin/mongoid,jamesalmond/mongoid,ginty/mongoid,jetthoughts/mongoid,tolsen/mongoid,captain-lucas/mongoid,xentek/mongoid,mash-ltd/mongoid,alexandru-calinoiu/mongoid,caiofilipini/mongoid,i0rek/mongoid,nicolasblanco/mongoid,idesaku/mongoid,icambron/mongoid,grimen/mongoid,ryanong/mongoid,hbakhtiyor/mongoid,mhs/mongoid,crealytics/mongoid,flexoid/mongoid,atomical/mongoid,cgriego/mongoid,jstrocel/mongoid,mzsanford/mongoid,jmaicher/mongoid