Add several commonly used plugins

I'm too lazy to use Pathogen, so I've just linked the source in the .vim
folder.

Plugins in use are:

- GitGutter
- Solarized colorscheme (sometimes)
- Vim-Airline*
- Syntastic*
- NERDTree*
- Tabular*

* Not included in .vim- installed via package manager

Tested-on: arcturus <10 Feb 2014>