Migrate plugin manager from Pathogen to Vundle

### Features
* [Vundle](https://github.com/gmarik/Vundle.vim) handles installation from vimrc and simplifies updating
* README has been updated for full installation
* All existing plugins are configured in vimrc
* Compliant with Vundle's [new "Plugin" interface](https://github.com/gmarik/Vundle.vim/blob/v0.10.2/doc/vundle.txt#L372-L396)

### Consequences
* Makes future plugin install/uninstall much easier
* No longer using git submodules (!!)
* Checkout/install instructions require an extra git clone
* Installation is mostly watching :PluginInstall in Vim

### Testing
* Tested on moss from nuked ~/.vim (left symlinks intact)
* YouCompleteMe on moss has huge startup time - suggest using ^Z or commenting it out