Use rcm instead of ./install.sh

The rcm suite is designed to replace the `./install.sh` script found in
this and many other dotfiles repos across GitHub. By using rcm users can
combine multiple dotfiles repos, tag dotfiles, have host-specific
dotfiles, and other powerful features.

This commit removes `install.sh`, updates the README, adds a post-up
hook that vundles the vim bundles, and adds a `rcrc` configuration that
ignores `README.md` and `LICENSE` and sets the dotfiles directory to
just `dotfiles`.
Add Git credentials.
Initialise rbenv on startup.
Add Homebrew directory to PATH.
Move personal details to local files.
Add Github Enterprise settings.
Add Github CLI.
Look for GitHub Enterprise settings.
Initialise rvm, if it's installed