Vim: Add Syntastic

Once upon a time I had used the syntastic plugin but gave up on it after
it stopped working properly. Now, it seems to be working again so I'm
going to give it another spin. I've configured it similarly to @sds,
who's settings I've borrowed from:

  https://github.com/sds/.vim/blob/master/config/plugins/syntastic.vim
Scripts: add update script

This script turns bringing all of my submodules up to date and updating
command-t into a one step process.
Update submodules

This gets me on the latest versions of my plugins. Included are
syntastic, ultisnips, and vimrails.
Vim: set nocompatible

According to a post on stackoverflow[1], `set nocompatible` isn't
completely useless. Adding it back to my .vimrc to be safe, rather than
sorry.

Note that this must come before other `set` calls because setting this
magically wipes out anything that was set before it. Therefore, I put
this as the first line in my .vimrc instead of where all of my other
settings are, which is currently .vim/plugin/settings.vim.

[1]: http://stackoverflow.com/a/5845583/18986
Vim: move ultisnips config to own file

In an attempt to keep my .vimrc file clean and have everything
organized, I'm moving my ultisnips configuration out of .vimrc and into
its own file in .vim/plugin/ultisnips.vim.