Added a new script that can be used to update the repo if bash is
available. Updated the README. Improved the theme by adding a bunch
of syntax highlighting definitions (mostly rooted in html, though
a bunch of other languages base their colours on it), as well as
tweaking visual selection to longer invert on the block with the cursor,
and parenthesis matching to look the same at both ends. Added a plugin
that improves the theme and adds some keyboard shortcuts to markdown,
which is what the README.md files in Github are written in. I realized
that the h,j,k,l shortcuts equivalent to the ones with arrow keys I'd
added were overwriting other shortcuts with the shift combinations, so
I removed those and the ctrl-ones for consistency. The diff shortcuts
weren't intuitive or easy on the hands, so I tried something else and
I think it works much better now (check vim/keyboard.vim). An update
script has also been added to simplify updating submodules; I'm not
completely clear as to whether following this method will properly
update the submodules in certain conditions like when one is removed,
but this should add new ones and update the existing ones after pulling
from the repo.