Update setup.sh to use ruby-install for installing Rubies.
Merge pull request #171 from havenwood/setup

Update setup.sh to use ruby-install for installing Rubies.
Style.
Added RUBY_INSTALL_VERSION.
No need to set RUBIES anymore.
Fix typo in comments.
Match whitespace to current Formula on Homebrew.
Example of non-standard location.

This was the only remaining difference with Homebrew's accepted chruby formula. So now with this change Homebrew's formula is identical to this formula.