TST : removed no-op test files
TST : added __main__ method to all test files
Merge pull request #206 from ericdill/version

MNT: Updated setup.py
Merge pull request #202 from tacaswell/test_maintence

Test maintence
MNT: Cleaned up package list in setup.py
MNT: Replaced package with the correct one
MNT: Refactor of constants.py

- Created constants sub-module
- Created api.py file in constants submodule that provides a
  clean entry point into our constants objects/functions
- Created BasicElement class that holds basic element information
- Created XrfElement class that subclasses BasicElement and adds
  X-ray fluorescence information
- Moved Xray scattering calibration stuff into xrs.py module. Will
  probably end up moving that somewhere else

MNT: Removed neutron.py from constants/