First stab at fixing OpenMM CHARMM parsers with NBFIX.
Add test cases for NBFIX for both the chamber action and the CharmmPsfFile. The
only bug really was in the OpenMMCharmmPsfFile (which I hope to absorb into
Structure at some point... that would be nice).
Add missing test files.
Merge pull request #16 from swails/fix_charmm_openmm

Fix charmm openmm. This should fix #15