update to latest pysam
Revert "update to latest pysam"

This reverts commit 25b4ffbadb1787d22a14a3fb5c893e53426e3f7e.
update to 0.8.1, but dont include the other edits
Merge pull request #50 from broadinstitute/dp-pysam081

upgrade pysam to 0.8.1