implement additional tests for groupby apply methods
implement additional tests for groupby apply methods

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