[vim] Night of the long knives

- Added autocommand to auto-clean up fugitive buffers.
[vim] Say hello to unimpaired

- Added vim-unimpaired
- Remapped extra non-US keyboard keys
[vim] Wednesday, bloody wednesday

- Removed powerline in favour of a more simplified statusline.
- Removed automatic sourcing of vimrc after writing.
- Minor tweaks to window heights and company.