Documentation upgrade

This package was lacking real documentation, it is fixed in this version.

Added

• Sphinx documentation!
• Web site hosted on GitHub pages, check hugofara.github.io/leggedsnake!
• Expanded README with quick links.

Changed

• Tests moved from leggedsnake/tests to tests/.
• Examples moved from leggedsnake/examples/ to docs/examples/
• I was testing my code on leggedsnake/examples/strider.py (old path) and that's why it was a big mess. I cleaned up that all. Sorry for the inconvenience!

Fixed

• A lot of outdated code in the leggedsnake/examples/strider.py (old path).
• Changelog URL was broken in setup.cfg.