Began merging multiple codepaths.
Deleted duplicate tests.
Removed head_node bool as everything has mpicomm.rank now.
Removed generate_maxwell_boltzmann re issue #28
Working MPI tests and some minor shuffling.
Added support for string input to ThermodynamicState init()
Fixed most of import simtk.openmm
Fixed rest of openmm.
Moved tests of all testsystems from testsystems.py to nose.
Minor bugfix
Moved str_to_system into utils and reverted Thermostate init
Only test the fast testsystems.
ThermodynamicState requires system and temperature, plus docstring cleanup.
Added pkg_resources support in testsystems re issue #33
Added mpiexec search for nose tests.
Fixed MPI test skipping.
Merge pull request #26 from choderalab/mpitests

Began merging multiple codepaths.