Refactor exceptions.py to pysynexcept.py and fix usage.  Avoids clobbering Python exceptions module in the namespace.  Addresses issue #19.
Merge pull request #1 from chanley/exceptions

Refactor exceptions.py module.  Will address issue #19 at spacetelescope/pysynphot.  Python 3 builds still fail.
update .gitignore file
Modify imports, make them explicit relative imports.  Cleanup namespace in Cache.py.
Modify imports, make them explicit relative imports.  Cleanup namespace in catalog.py.
Cleanup namespace in graphtab.py.
Cleanup namespace in locations.py.
PEP8 fixes. Make imports explicit relative imports. Cleanup namespace in obsbandpass.py.
Turn off Python 3.x testing for now.

PEP8 fixes. Make imports explicit relative imports.

 Cleanup namespace in observation.py.
Make all imports explicit relative imports.  Clean up namespace.
Make all imports explicit relative imports.  Clean up namespace in reddening.py.
Make all imports explicit relative imports.  Clean up namespace in refs.py.
Make all imports explicit relative imports.  Clean up namespace in renorm.py.
Make all imports explicit relative imports.  Clean up namespace in reseltable.py.
Make all imports explicit relative imports.  Clean up namespace in spectrum.py.
Make all imports explicit relative imports.  Clean up namespace in spparser.py.
Clean up namespace in tables.py.
Change imports in units.py to be relative explicity imports.  Define a Vega class in spectrum.py.
Merge pull request #22 from chanley/master

Python3 support, circular reference, PEP8 cleanup