Revert `gh` to `hub`

`hub`, like `gh`, is now powered by `go`.

https://github.com/github/hub#2x

Since `gh` is a GitHub CLI, why not use the CLI created by GitHub themselves.

Additionally, `hub` handles `$ git clone thoughtbot/laptop` out of the box.
2.2.0 rc1 released: https://github.com/github/hub/releases/tag/v2.2.0-rc1

Homebrew still requires HEAD. I agree on waiting until 2.x is stable and
the Homebrew package is updated.

On Thu, Dec 18, 2014 at 2:26 PM, pat brisbin <notifications@github.com>
wrote:

> In mac
> <https://github.com/thoughtbot/laptop/pull/346#discussion-diff-22076414>:
>
> > @@ -129,7 +129,7 @@ fancy_echo "Installing QT, used by Capybara Webkit for headless Javascript integ
> >    brew_install_or_upgrade 'qt'
> >
> >  fancy_echo "Installing GitHub CLI client ..."
> > -  brew_install_or_upgrade 'gh'
> > +  brew_install_or_upgrade 'hub --head'
>
> Should we wait until it's out of preview before making this change?
>
> What is going to happen to gh?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/thoughtbot/laptop/pull/346/files#r22076414>.
>