Rewrite completely and rename to Colemakerel.

This is more or less a complete overhaul of the plugin, and there's
little to no progression between the old and new versions, so I'm just
swapping them in one huge commit.

I'm renaming the project while I'm at it. Might as well give it some
character.

Major changes:
- Now uses langmap to do most of the heavy lifting. Combined with some
  fancypants metaprogramming, this let me drastically reduce the
  plugin's size. On the flip side, using langmap breaks some stuff that
  worked with mappings, like menus and mappings. This will have to be
  addressed.
- Re-released under the BSD 3-Clause License.