Remove ruby-install as a submodule

- It is not a direct dependency for my dotfiles, as you can run my vim
  config and everything without Ruby. It's more of a "nice-to-have" and
  therefore should be a separate install.
Un-hide all files

There's no reason for the dotfiles repo to contain hidden (dot-prefixed)
files, as when we copy them over to ~ we can rename them to be whatever
we want. This makes it much easier to manage, especially on OSX (where
Finder's a little bitch).