Fix behavior of `to_offset` with leading zeroes
Fix behavior of `to_offset` with leading zeroes

Currently, `pandas.tseries.frequencies.to_offset` erroneously returns a zero time offset when the first part of its argument has a numerical value of zero, even if later parts have nonzero values.  For instance,

    In [123]: pandas.tseries.frequencies.to_offset('00H 00T 01S')
    Out[123]: <0 * Days>

In this patch the sign check is applied before conversion to `int` in order to support offsets like `'-00H 00T 01S'`.
jreback/pandas,louispotok/pandas,cython-testbed/pandas,jreback/pandas,linebp/pandas,nmartensen/pandas,jmmease/pandas,dsm054/pandas,nmartensen/pandas,cython-testbed/pandas,jorisvandenbossche/pandas,harisbal/pandas,jmmease/pandas,pandas-dev/pandas,jmmease/pandas,cbertinato/pandas,cython-testbed/pandas,cbertinato/pandas,jorisvandenbossche/pandas,winklerand/pandas,louispotok/pandas,nmartensen/pandas,rs2/pandas,pandas-dev/pandas,DGrady/pandas,dsm054/pandas,TomAugspurger/pandas,toobaz/pandas,gfyoung/pandas,kdebrab/pandas,jreback/pandas,kdebrab/pandas,GuessWhoSamFoo/pandas,pandas-dev/pandas,zfrenchee/pandas,cython-testbed/pandas,kdebrab/pandas,jmmease/pandas,louispotok/pandas,linebp/pandas,cbertinato/pandas,linebp/pandas,datapythonista/pandas,gfyoung/pandas,toobaz/pandas,jorisvandenbossche/pandas,rs2/pandas,jmmease/pandas,MJuddBooth/pandas,cbertinato/pandas,gfyoung/pandas,amolkahat/pandas,TomAugspurger/pandas,jreback/pandas,amolkahat/pandas,pratapvardhan/pandas,DGrady/pandas,dsm054/pandas,toobaz/pandas,MJuddBooth/pandas,gfyoung/pandas,rs2/pandas,TomAugspurger/pandas,MJuddBooth/pandas,Winand/pandas,pratapvardhan/pandas,Winand/pandas,pratapvardhan/pandas,dsm054/pandas,pratapvardhan/pandas,harisbal/pandas,winklerand/pandas,linebp/pandas,GuessWhoSamFoo/pandas,MJuddBooth/pandas,linebp/pandas,zfrenchee/pandas,DGrady/pandas,zfrenchee/pandas,amolkahat/pandas,kdebrab/pandas,DGrady/pandas,Winand/pandas,winklerand/pandas,jmmease/pandas,DGrady/pandas,TomAugspurger/pandas,nmartensen/pandas,pandas-dev/pandas,GuessWhoSamFoo/pandas,louispotok/pandas,Winand/pandas,nmartensen/pandas,kdebrab/pandas,cython-testbed/pandas,GuessWhoSamFoo/pandas,dsm054/pandas,cbertinato/pandas,louispotok/pandas,GuessWhoSamFoo/pandas,datapythonista/pandas,amolkahat/pandas,zfrenchee/pandas,Winand/pandas,jorisvandenbossche/pandas,harisbal/pandas,rs2/pandas,datapythonista/pandas,toobaz/pandas,toobaz/pandas,winklerand/pandas,datapythonista/pandas,jreback/pandas,amolkahat/pandas,DGrady/pandas,winklerand/pandas,winklerand/pandas,harisbal/pandas,harisbal/pandas,MJuddBooth/pandas,zfrenchee/pandas,nmartensen/pandas,linebp/pandas,gfyoung/pandas,pratapvardhan/pandas,Winand/pandas