added overrideable managed_attribute_dict() function which can be changed to eliminate circular references on objects
added overrideable managed_attribute_dict() function which can be changed
to eliminate circular references on objects

sqlalchemy/sqlalchemy,alex/sqlalchemy,ThiefMaster/sqlalchemy,brianv0/sqlalchemy,monetate/sqlalchemy,robin900/sqlalchemy,EvaSDK/sqlalchemy,davidfraser/sqlalchemy,olemis/sqlalchemy,wfxiang08/sqlalchemy,j5int/sqlalchemy,276361270/sqlalchemy,olemis/sqlalchemy,WinterNis/sqlalchemy,Cito/sqlalchemy,Cito/sqlalchemy,inspirehep/sqlalchemy,bootandy/sqlalchemy,pdufour/sqlalchemy,graingert/sqlalchemy,davidjb/sqlalchemy,j5int/sqlalchemy,WinterNis/sqlalchemy,itkovian/sqlalchemy,hsum/sqlalchemy,monetate/sqlalchemy,ThiefMaster/sqlalchemy,inspirehep/sqlalchemy,pdufour/sqlalchemy,wujuguang/sqlalchemy,hsum/sqlalchemy,graingert/sqlalchemy,sandan/sqlalchemy,davidjb/sqlalchemy,brianv0/sqlalchemy,alex/sqlalchemy,Akrog/sqlalchemy,276361270/sqlalchemy,wujuguang/sqlalchemy,bootandy/sqlalchemy,halfcrazy/sqlalchemy,bdupharm/sqlalchemy,dstufft/sqlalchemy,elelianghh/sqlalchemy,wfxiang08/sqlalchemy,epa/sqlalchemy,zzzeek/sqlalchemy,dstufft/sqlalchemy,robin900/sqlalchemy,Cito/sqlalchemy,itkovian/sqlalchemy,elelianghh/sqlalchemy,alex/sqlalchemy,Akrog/sqlalchemy,EvaSDK/sqlalchemy,halfcrazy/sqlalchemy,davidfraser/sqlalchemy,bdupharm/sqlalchemy,epa/sqlalchemy,sandan/sqlalchemy