Move Bundles into a separate file

I've had this in [my own dotfiles] for a while now, and really like
having the separation of what I consider to be code/configuration from
what to me feels more like a Gemfile, in that it lists out all of the
external dependencies in a single place.

[my own dotfiles](https://github.com/calebthompson/dotfiles/blob/master/vim/vimrc.bundles.symlink)

* Awesomer vundle integration:
  * Refactor .vimrc and .vimrc.bundles to support standalone
    BundleInstall.
  * Install vim bundles as part of install.sh without sourcing the
    normal vimrc, which prevents error messages from uninstalled
    plugins referenced in the main vimrc.