Refactored to lots of teensy functions

To try out this way of programming. Every function has one small job
Rename some functions for simpler names
pep8, rename/expose some functions, add docs

Expose the functions for creating data/gist URLs and for parsing
the contents to the GeoJSON string.
Initial commit of test_geojsonio.py
Incorporate six and get working for 2.6, 2.7, 3.3
Initial commit of tox.ini
Initial commit of .travis.yml
README.md -> README.rst