Refactor `install_dotfiles`
Migrate vim config

Squashed commit of the following:

commit b758c60785062992bbea1e22e645a00ab849ccb3
Author: T.S. Foster <hi@tsf.io>
Date:   Sun Sep 28 23:51:19 2014 +0100

    Add requirements to README.md

commit 9bd061d39c163bb2422e85bfa5c9d13cbc11e4e2
Author: T.S. Foster <hi@tsf.io>
Date:   Sun Sep 28 23:51:05 2014 +0100

    Migrate vim config

commit 56f81062fe14dc09cc1292968b3adf80ee0dea56
Author: T.S. Foster <hi@tsf.io>
Date:   Fri Sep 26 14:01:59 2014 +0100

    Install Vundle & extensions in `install_dotfiles`

commit 05200719d395845621a7c2e303404138579f0831
Author: T.S. Foster <hi@tsf.io>
Date:   Fri Sep 26 13:15:21 2014 +0100

    Setup vim directory, sourcing old vim files