minor fixes
Removed import of attic'd things from sandbox.
Merge pull request #31 from dwhswenson/master

Removed import of attic'd things from sandbox.
Merge branch 'master' of github.com:choderalab/msm-tis
gitignore inside src.

For future reorg; ignores *pyc and tags.
Fixed wrong logic in forward/backward and added more intelligent treatment of negation of volume based ensembles
Merge pull request #34 from jhprinz/ensemble-fw/bw

Ensemble negation corrections
Merge remote-tracking branch 'origin/master' into enter_exit_ensembles
Merge remote-tracking branch 'upstream/master' into enter_exit_ensembles

Conflicts:
	code/python/PySRMSTIS/src/ensemble.py