Moved tests into separate repex/tests/ directory.
Merge pull request #6 from jchodera/master

Moved tests into separate repex/tests/ directory
Added reduced potential energy to tests re issue #8
Added Nij accumulation for issue #7
Added a harmonic oscillator test.
Cleanup in test.
Fixed tests to work with new repex organization containing testsystems.
Fixed an undefined global parameter in Diatom that caused an error when use_central_potential=True
Added AlanineDipeptideVacuum and fixed issues with how constraints were specified for AlanineDipeptide* systems.  Note that arguments have now changed for these systems.
Updated custom integrator test.
Fixed tracking and reporting in integrator test.
Added working test of HREX using power oscillators.
Added simple tests for save and load functionality.
Trying to un-break renamed directory structure for easier merge...
Better name for test-nose dir
Working PT and tests.
Rename some tests.
Major updates to custom integrator testing.
Cleaned up all custom integrators from tests/test_custom_integrators.py and put them in a new file: repex/integrators.py
Updated custom integrator tests to use new integrators.py