telephone_to method

You might have heard that HTML5 added the `mailto` and `tel`. I was able to find a `mail_to` method inside of Rails, but there didn't seem to be anything for `telephone_to`.

In this PR, I took the time to provide a method to generate telephone links that will add pauses, optimize for pause separators/phone extensions, and even let you add a `skype: true` option.

See the examples above the method for what you can do with it here.