Shell of a file for unit tests, to be used with nose2
Initial tests

data/test.gms -- example file to generate a GDX for testing.
.gitignore -- ignore the GDX and listing files generated.
gdx/tests.py -- the tests.

gdx/__init__.py
- Add property decorator on Set.depth
- BUG: range() too small in loading symbols, resulted in last symbol in
  file being omitted (fixed).
Refactor to use pandas data structures
Remove unused enumarray class/file, unused imports, and de-flake
Refactoring and improve inline documentation

gdx/__init__.py
- Rename all load() methods to _load()
- Prevent recursion in Symbol._load()
- Load GAMS set element explanatory text in Set._load()
- Convenience methods to underlying pandas data structures in Set,
  Parameter
Improve documentation
Merge pull request #1 from khaeru/pandas

Use pandas data structures.