Use my fork of vim-protobuf with a better syntax file.

@matthewtodd @strongriley 

### Before
![badproto](https://f.cloud.github.com/assets/1938/1205292/1aaa8e66-257d-11e3-8252-4848998ba161.png)

### After
![goodproto](https://f.cloud.github.com/assets/1938/1205293/23175be2-257d-11e3-8c8b-6b1177e6ed51.png)