The source files are now concatenated in order in which they are
required in lib/hub.rb

closes #84

Apart from "-t" not being supported by zsh's `type`, it does not appear
to work with bash, too.

Fixes: http://github.com/defunkt/hub/issues/#issue/47

tests now simulate ruby platform and commands being present
or missing on the system.

Fixed a problem in the ronn file this caused.

Usage example:

  $ git fork
  (forks "defunkt/hub" on GitHub)
  (git remote add mislav git@github.com:mislav/hub.git)
  new remote: mislav

Use `git fork --no-remote` to skip adding the new remote.

Tests use Webmock for stubbing out HTTP requests:

  $ gem install webmock

pages.

caveat: had to override jewelers install task

(homebrew). Just build the standalone script no matter.