BUG: coerce ndarray dtype to object when comparing series
BUG: coerce ndarray dtype to object when comparing series

fixes #1926 (partialy at least)

pandas-dev/pandas,pratapvardhan/pandas,rs2/pandas,datapythonista/pandas,zfrenchee/pandas,datapythonista/pandas,dsm054/pandas,cython-testbed/pandas,harisbal/pandas,dsm054/pandas,Winand/pandas,zfrenchee/pandas,MJuddBooth/pandas,kdebrab/pandas,pratapvardhan/pandas,gfyoung/pandas,DGrady/pandas,GuessWhoSamFoo/pandas,jmmease/pandas,jreback/pandas,gfyoung/pandas,winklerand/pandas,kdebrab/pandas,toobaz/pandas,jmmease/pandas,pandas-dev/pandas,louispotok/pandas,nmartensen/pandas,toobaz/pandas,Winand/pandas,pratapvardhan/pandas,rs2/pandas,linebp/pandas,winklerand/pandas,GuessWhoSamFoo/pandas,jmmease/pandas,rs2/pandas,jorisvandenbossche/pandas,amolkahat/pandas,DGrady/pandas,Winand/pandas,linebp/pandas,jmmease/pandas,MJuddBooth/pandas,jmmease/pandas,nmartensen/pandas,kdebrab/pandas,jmmease/pandas,gfyoung/pandas,jorisvandenbossche/pandas,kdebrab/pandas,winklerand/pandas,datapythonista/pandas,cbertinato/pandas,toobaz/pandas,jreback/pandas,cython-testbed/pandas,toobaz/pandas,pratapvardhan/pandas,amolkahat/pandas,louispotok/pandas,winklerand/pandas,harisbal/pandas,amolkahat/pandas,pratapvardhan/pandas,cbertinato/pandas,DGrady/pandas,rs2/pandas,GuessWhoSamFoo/pandas,nmartensen/pandas,cython-testbed/pandas,TomAugspurger/pandas,MJuddBooth/pandas,jreback/pandas,linebp/pandas,datapythonista/pandas,zfrenchee/pandas,TomAugspurger/pandas,linebp/pandas,pandas-dev/pandas,nmartensen/pandas,linebp/pandas,zfrenchee/pandas,dsm054/pandas,DGrady/pandas,Winand/pandas,zfrenchee/pandas,Winand/pandas,dsm054/pandas,kdebrab/pandas,jreback/pandas,jorisvandenbossche/pandas,winklerand/pandas,harisbal/pandas,jreback/pandas,harisbal/pandas,gfyoung/pandas,cython-testbed/pandas,cython-testbed/pandas,cbertinato/pandas,Winand/pandas,DGrady/pandas,dsm054/pandas,GuessWhoSamFoo/pandas,MJuddBooth/pandas,amolkahat/pandas,linebp/pandas,DGrady/pandas,harisbal/pandas,jorisvandenbossche/pandas,MJuddBooth/pandas,TomAugspurger/pandas,cbertinato/pandas,louispotok/pandas,gfyoung/pandas,TomAugspurger/pandas,nmartensen/pandas,winklerand/pandas,toobaz/pandas,pandas-dev/pandas,GuessWhoSamFoo/pandas,amolkahat/pandas,nmartensen/pandas,cbertinato/pandas,louispotok/pandas,louispotok/pandas