tweetLink() now returns a Twig_Markup object

This removes the need to pass the resulting string through the |raw filter.

TemplateHelper::getRaw() is a new Craft 2.0 feature, so if you use this you should probably update the Readme to note that it requires Craft 2.0.
Merge branch 'master' of https://github.com/marionnewlevant/craft-tweetlinker
brandonkelly-patch-2