add a note about native unicode mode, [ticket:1792]
add a note about native unicode mode, [ticket:1792]

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