Generalized WaterBox test to allow other water models to be specified.
Added subclasses for convenience construction of four- and five-site waters.
Merge pull request #42 from jchodera/improved-waterbox-testsystems

Generalized WaterBox test to allow water model to be specified. Valid choices are tip3p, tip4pew, tip5p, spce.  No AMOEBA water support yet.
Merge pull request #43 from jchodera/master

Fixed bug that prevented running tests/test_platforms.py due to way in which test classes were queried.
Added tests for PT and HE sanity check.
Updated docstring on HE sanity check.
Changed states to thermodynamic_states for clarity.
Updated HE, PT, RE, and minor tests.
Cleaned up some extra commented out code.
Cleared one more comment
Changed the comment style on block comment for clarity in the diff.
First checkin of general MCMC move approach.
Fixed minimize docstring in mcmc.py
Added NAN detection helper function to mcmc.py, also general cleanup.
Minor cleanup.
Updates
Minor cleaning up in test
Load in system from the thermodynamic state before MCMCSampler.run()
Fixed pressure issue.
Merge pull request #51 from choderalab/fullmcmc

[WIP] Full MCMC support