Add documentation on readonly error
Add documentation on readonly error

nusco/mongoid,herimedia/mongoid,drobune/mongoid,simi/mongoid,zaithottakath/mongoid,narutosanjiv/mongoid,wuboy0307/mongoid,codedogfish/mongoid,mongodb/mongoid,eljojo/mongoid,johnny-miyake/mongoid,bjori/mongoid,mongodb/mongoid,parov/mongoid,mysociety/mongoid,eljojo/mongoid,imomoisoft/mongoid,asantamar/mongoid,karmakaze/mongoid,hashrocketeer/mongoid,estolfo/mongoid,cao7113/mongoid,Sharevari-Inc/mongoid,glebtv/mongoid,subhashb/mongoid,Zhomart/mongoid,amw/mongoid,joshsoftware/mongoid,johnny-miyake/mongoid,stnguyen/mongoid,rafaelgaspar/mongoid,Azzurrio/mongoid,mysociety/mongoid,kayakyakr/mongoid,wuboy0307/mongoid,arnkorty/mongoid,matbox/mongoid,zaithottakath/mongoid,kcdragon/mongoid,itbakery/mongoid,jonhyman/mongoid,Welovroi/mongoid,canvas-drw/mongoid,jbrien/mongoid,bencrouse/mongoid,nusco/mongoid,nicolasblanco/mongoid,herimedia/mongoid,rpocklin/mongoid,Azzurrio/mongoid,zBMNForks/mongoid,matbox/mongoid,canvas-drw/mongoid,hashrocketeer/mongoid,codedogfish/mongoid,nviennot/mongoid,trmmy/mongoid,rafaelgaspar/mongoid,parov/mongoid,zBMNForks/mongoid,mongoid/mongoid,jonhyman/mongoid,rinmu/mongoid,amw/mongoid,glebtv/mongoid,demarque/mongoid,subhashb/mongoid,kayakyakr/mongoid,infiverve/mongoid,sivagollapalli/mongoid,joshsoftware/mongoid,bjori/mongoid,itbakery/mongoid,mongodb/mongoid,karmakaze/mongoid,kay-kim/mongoid,jbrien/mongoid,sideci-sample/sideci-sample-mongoid,zenjoy/mongoid,demarque/mongoid,tzar/mongoid,bencrouse/mongoid,sideci-sample/sideci-sample-mongoid,kay-kim/mongoid,cao7113/mongoid,arnkorty/mongoid,uniiverse/mongoid,sivagollapalli/mongoid,uniiverse/mongoid,hxx/mongoid,infiverve/mongoid,asantamar/mongoid,tzar/mongoid,Zhomart/mongoid,estolfo/mongoid,stnguyen/mongoid,rpocklin/mongoid,nviennot/mongoid,imomoisoft/mongoid,mongoid/mongoid,zenjoy/mongoid,narutosanjiv/mongoid,kcdragon/mongoid,hxx/mongoid,drobune/mongoid,Welovroi/mongoid,Sharevari-Inc/mongoid,rinmu/mongoid,simi/mongoid,trmmy/mongoid