Fixed DateRange.union logic, docs, changed XDateRange class to a generator function
Fixed DateRange.union logic, docs, changed XDateRange class to a generator function

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