Don't require rack/mongoid. It was removed with IdentityMap (7180173).
Don't require rack/mongoid. It was removed with IdentityMap (7180173).

Fix #3367.

kuadrosx/mongoid,Sharevari-Inc/mongoid,dustinwatson/mongoid,infiverve/mongoid,mysociety/mongoid,estolfo/mongoid,greggroth/mongoid,amw/mongoid,kcdragon/mongoid,karmakaze/mongoid,glebtv/mongoid,mongoid/mongoid,wuboy0307/mongoid,PerfectMemory/mongoid,Numerico/mongoid,jonhyman/mongoid,abezzub/mongoid,bjori/mongoid,trmmy/mongoid,simi/mongoid,drobune/mongoid,bjori/mongoid,PerfectMemory/mongoid,timgluz/mongoid,robwil/mongoid,hashrocketeer/mongoid,kcdragon/mongoid,charliehq/mongoid,amw/mongoid,Welovroi/mongoid,sivagollapalli/mongoid,estolfo/mongoid,zBMNForks/mongoid,uniiverse/mongoid,rpocklin/mongoid,parov/mongoid,stnguyen/mongoid,aj0strow/mongoid,mattconnolly/mongoid,subhashb/mongoid,glebtv/mongoid,krasnoukhov/mongoid,rubrikkfabrikken/mongoid,tricknotes/mongoid,tzar/mongoid,abezzub/mongoid,herimedia/mongoid,subhashb/mongoid,praecipula/mongoid,CIRCUITLLC/mongoid,sideci-sample/sideci-sample-mongoid,imomoisoft/mongoid,arnkorty/mongoid,aj0strow/mongoid,uniiverse/mongoid,nicolasblanco/mongoid,zaithottakath/mongoid,imomoisoft/mongoid,tricknotes/mongoid,X0nic/mongoid,demarque/mongoid,robwil/mongoid,rubrikkfabrikken/mongoid,hbakhtiyor/mongoid,parov/mongoid,Numerico/mongoid,nviennot/mongoid,kay-kim/mongoid,kayakyakr/mongoid,elia/mongoid,jbrien/mongoid,johnny-miyake/mongoid,greggroth/mongoid,kayakyakr/mongoid,arnkorty/mongoid,trmmy/mongoid,canvas-drw/mongoid,zaithottakath/mongoid,eljojo/mongoid,dustinwatson/mongoid,kentaroi/mongoid,nusco/mongoid,codedogfish/mongoid,mongodb/mongoid,krasnoukhov/mongoid,CIRCUITLLC/mongoid,nviennot/mongoid,sideci-sample/sideci-sample-mongoid,Zhomart/mongoid,Zhomart/mongoid,zBMNForks/mongoid,Sharevari-Inc/mongoid,rinmu/mongoid,itbakery/mongoid,bencrouse/mongoid,wuboy0307/mongoid,X0nic/mongoid,codedogfish/mongoid,infiverve/mongoid,hashrocketeer/mongoid,mattconnolly/mongoid,drobune/mongoid,elia/mongoid,mysociety/mongoid,charliehq/mongoid,nusco/mongoid,itbakery/mongoid,hbakhtiyor/mongoid,kuadrosx/mongoid,demarque/mongoid,rpocklin/mongoid,etomic/mongoid,rinmu/mongoid,jasl/mongoid,jbrien/mongoid,stnguyen/mongoid,narutosanjiv/mongoid,tzar/mongoid,sivagollapalli/mongoid,kentaroi/mongoid,chetan/mongoid,jtescher/mongoid,Azzurrio/mongoid,mongodb/mongoid,zenjoy/mongoid,Azzurrio/mongoid,cao7113/mongoid,zenjoy/mongoid,bencrouse/mongoid,Welovroi/mongoid,jtescher/mongoid,mongoid/mongoid,simi/mongoid,kay-kim/mongoid,rafaelgaspar/mongoid,jasl/mongoid,herimedia/mongoid,asantamar/mongoid,praecipula/mongoid,narutosanjiv/mongoid,chetan/mongoid,etomic/mongoid,hxx/mongoid,hxx/mongoid,asantamar/mongoid,cao7113/mongoid,joshsoftware/mongoid,timgluz/mongoid,johnny-miyake/mongoid,canvas-drw/mongoid,mongodb/mongoid,karmakaze/mongoid,joshsoftware/mongoid,rafaelgaspar/mongoid,eljojo/mongoid,matbox/mongoid,matbox/mongoid,jonhyman/mongoid