Fix vim plugin path in Arch Linux packages
Add note about zpython branch

TODO: To be removed after (if) zsh maintainers accept the patch.

Refs #104.
Add modified_buffers segment

This segment returns a comma-separated list of modified buffers. The
segment is not enabled by default.

Closes #173.
Use functools.wraps on memoize decorator
Update sphinx configuration
Work around missing vim module when generating sphinx docs

Horrible solution, should be fixed asap.
Add docs for all segments