Expand `au` to `autocmd` and remove duplication.
Support Ruby 1.8 in the init script.
Update zprezto.
Rewrite the symlinking.

This accidentally fixes a bug where a folder `foldername` would be symlinked to
`foldername/foldername`, which was pointless and annoying.
Add a vim plugin to read and write GnuPG-encrypted files.