Add a test for chemistry/system.py
Have PDB files with 1 model report models=1 rather than 0
Add more tests.
More tests and fix the package names in chemistry/tinker
Add a test for Tinker .dyn files.
- Fix issue where testing whether a bond was contained in an Angle in a
  CharmmPsfFile would return false positives
- Fix testing whether a bond was inside a UreyBradley in a ChamberParm object
  (leftover from reverting API changes)
- Fix PSF parsing for PSF files that don't strictly conform to (expected)
  formats.
- Improve error messages for debugging PSF parsing problems.
- Delete some test files (getting moved to the unit test file directory)
Expand test coverage for the Amber objects
Add tests for the CHARMM functionality
Add test files
More extensive parameter set tests.
Add tests for PSF file writing.
Add tests for writing (as well as more rigorous tests for reading) Amber
coordinate files.
Add tests for the file writing routines, and check some of the error checking
as well.