Add vim 7.4.453.

Windows only at the moment.  Enables DirectX/DirectWrite font rendering
support, which, among other things, makes fonts tolerable to look at when
being viewed over Citrix (where GDI/ClearType font smoothing doesn't work).

Tweaked the default colorscheme and config because, hey, it can't get any
worse than how gvim ships on Windows by default.

The build has been configured with Python as a dependency, and there is some
plugin support for some small-but-useful helpers when you're working on Python
files.

Pre-built version:

    conda install -c trent vim