Added custom theme for the documentation.

The theme is based on Hangulize, by Heungsub Lee, and has its own
submodule hosted on GitHub.

There have also been many changes to the sphinx configuration and the
.rst source files to accomodate the changes. Hopefully the current
state serves as enough of a basis for the future.

Signed-off-by: Atheriel <atheriel@gmail.com>
Merge pull request #1 from atheriel/doc-theme

Added custom theme for the documentation.