Revert "Don't use `rvm`"

This reverts commit 30b2472b6c96f97836fc1f6f59501717ea614380.
Fix `aptitude` config
`dotfiles` should ignore `.gitignore` files
Tidied `aptitude` config
Added some apt config
Revert "Fix `aptitude` config"

This reverts commit deacc0d60b1f54453feec7391ce88cc0eaa61668.