Added support for Vundle

This pull request adds support for Vundle for installing bundles. It has two new files

* `~/.vimrc.bundles`
* `~/.vimrc.bundles.local`

The former includes all previous vim bundles and the latter enables the user to install their own packages. Vundle docs are here https://github.com/gmarik/vundle.

Please test this. I have used it on a Mac with 10.8.4.

This resolves #45.