Updated api docs
Updated api docs

fixes hmarr/mongoengine#526

elephanter/mongoengine,9nix00/mongoengine,starsirius/mongoengine,depop/mongoengine-stripped,yarneo/mongoengine,gmacon/mongoengine,WingGao/mongoengine,cogniteev/mongoengine,MakerReduxCorp/mongoengine,Davidrjx/mongoengine,MakerReduxCorp/mongoengine,reallistic/mongoengine,nathanial/mongoengine,eli-b/mongoengine,MongoEngine/mongoengine,khallaghi/mongoengine,losintikfos/mongoengine,prijindal/mongoengine,touilleMan/mongoengine,RussellLuo/mongoengine,ms5/mongoengine,Davidrjx/mongoengine,jimmyshen/mongoengine,ProgressivePlanning/mongoengine,sourcelair/mongoengine,larsbutler/mongoengine,MRigal/mongoengine,gavincabbage/mongoengine,muhammad-ammar/mongoengine,closeio/mongoengine,DavidBord/mongoengine,Catstyle/mongoengine,Multiposting/mongoengine,cogniteev/mongoengine,blaggacao/mongoengine,iandd0824/mongoengine,hmarr/mongoengine,nicolascine/mongoengine,ConsumerPhysics/mongoengine,noirbizarre/mongoengine