Basic top README changes to reflect the fork.
Rename repo_name to package_name.

* Rename to clarify that it's primarily the python package name.
Lean down on guides, and make it less github centric.
Let the package live in a 'lib' dir, and use requirements.txt for install_reqs.
Do most stuff with tox, to better handle dependencies.
Change sphinx theme and tweak the documentation output.
Simplify cookiecutter.json, and store version only once.
Handle namespace packages.
Remove 2.6 and pypy from travis.yml.
Simplify AUTHORS.rst.
Add headline differences from audreyr/cookiecutter-pypackage to top README.rst.