Refactored vimrc

- Removed a lot of unused things.
- Changed default colorscheme (I'll leave solarized as a backup).
- No more highlighting overlength lines (> 80 characters).

I also added the `lavalamp` colorscheme to vim/colors/ and the plugin
CSApprox for using GVim/MacVim colorschemes (lavalamp, in this case) in
terminal vim.