Replace neobundle with pathogen + shellscript

NeoBundle felt way too complex for what I needed,

I simply need a way to:
- list my plugins
- update them

Pathogen supports having multiple directories to have your plugins in.
I keep my "core" plugins in `~/.vim/bundles` and my ad-hoc ones in
`~/.vim/vendor`.
Update plugins inside `~/.vim/vendor`