Updated to_hdf doc string
Updated to_hdf doc string

Updated the docstring to make clear that a HDFStore is required for a buffer, if a path is not directly passed
cbertinato/pandas,cython-testbed/pandas,winklerand/pandas,harisbal/pandas,MJuddBooth/pandas,louispotok/pandas,linebp/pandas,GuessWhoSamFoo/pandas,zfrenchee/pandas,cbertinato/pandas,rs2/pandas,jmmease/pandas,cython-testbed/pandas,pandas-dev/pandas,dsm054/pandas,toobaz/pandas,amolkahat/pandas,cbertinato/pandas,dsm054/pandas,MJuddBooth/pandas,DGrady/pandas,gfyoung/pandas,harisbal/pandas,pratapvardhan/pandas,jorisvandenbossche/pandas,pandas-dev/pandas,amolkahat/pandas,linebp/pandas,DGrady/pandas,dsm054/pandas,GuessWhoSamFoo/pandas,MJuddBooth/pandas,TomAugspurger/pandas,winklerand/pandas,gfyoung/pandas,jreback/pandas,jreback/pandas,rs2/pandas,gfyoung/pandas,nmartensen/pandas,rs2/pandas,toobaz/pandas,datapythonista/pandas,TomAugspurger/pandas,DGrady/pandas,pratapvardhan/pandas,DGrady/pandas,pandas-dev/pandas,linebp/pandas,datapythonista/pandas,GuessWhoSamFoo/pandas,pratapvardhan/pandas,cython-testbed/pandas,winklerand/pandas,cython-testbed/pandas,jreback/pandas,linebp/pandas,datapythonista/pandas,MJuddBooth/pandas,jmmease/pandas,kdebrab/pandas,toobaz/pandas,cbertinato/pandas,Winand/pandas,nmartensen/pandas,Winand/pandas,linebp/pandas,zfrenchee/pandas,louispotok/pandas,gfyoung/pandas,linebp/pandas,kdebrab/pandas,cython-testbed/pandas,Winand/pandas,harisbal/pandas,louispotok/pandas,jmmease/pandas,DGrady/pandas,jreback/pandas,amolkahat/pandas,datapythonista/pandas,louispotok/pandas,gfyoung/pandas,pratapvardhan/pandas,MJuddBooth/pandas,jreback/pandas,louispotok/pandas,zfrenchee/pandas,toobaz/pandas,winklerand/pandas,jorisvandenbossche/pandas,winklerand/pandas,dsm054/pandas,jmmease/pandas,kdebrab/pandas,jmmease/pandas,Winand/pandas,Winand/pandas,TomAugspurger/pandas,zfrenchee/pandas,nmartensen/pandas,harisbal/pandas,rs2/pandas,dsm054/pandas,DGrady/pandas,GuessWhoSamFoo/pandas,winklerand/pandas,zfrenchee/pandas,amolkahat/pandas,Winand/pandas,nmartensen/pandas,amolkahat/pandas,jorisvandenbossche/pandas,harisbal/pandas,jorisvandenbossche/pandas,pandas-dev/pandas,cbertinato/pandas,pratapvardhan/pandas,kdebrab/pandas,nmartensen/pandas,kdebrab/pandas,toobaz/pandas,TomAugspurger/pandas,nmartensen/pandas,jmmease/pandas,GuessWhoSamFoo/pandas