Generate docs not from an already installed pysam
Generate docs not from an already installed pysam

Before, sys.path manipulation led to an already installed pysam version be
picked up by sphinx. Now, only the one in the build/ directory is used.

nlhepler/pysam,brendanofallon/pysam,dannon/pysam,mattions/pysam,carolinux/pysam,carolinux/pysam,kyleabeauchamp/pysam,dannon/pysam,kyleabeauchamp/pysam,mattions/pysam,TyberiusPrime/pysam,TyberiusPrime/pysam,daler/pysam,brendanofallon/pysam,mattions/pysam,mattions/pysam,daler/pysam,carolinux/pysam,brendanofallon/pysam,kyleabeauchamp/pysam,bioinformed/pysam,brendanofallon/pysam,TyberiusPrime/pysam,nlhepler/pysam,nlhepler/pysam,TyberiusPrime/pysam,kyleabeauchamp/pysam,TyberiusPrime/pysam,dannon/pysam,bioinformed/pysam,pysam-developers/pysam,pysam-developers/pysam,daler/pysam,dannon/pysam,nlhepler/pysam,bioinformed/pysam,carolinux/pysam,nlhepler/pysam,daler/pysam,carolinux/pysam,bioinformed/pysam,pysam-developers/pysam,pysam-developers/pysam,mattions/pysam,bioinformed/pysam,dannon/pysam,daler/pysam,brendanofallon/pysam,kyleabeauchamp/pysam