Support Github Flavored Markdown would be cool

I can't endorse this enough.

I'm constantly working in Markdown documents for...

• README files
• Wiki pages
• Guides
• Template Generation
• etc

The overwhelming majority of my Markdown docs are meant for GitHub, and those that aren't are either meant for implementation in Jekyll pages or are just miscellaneous documents.

Adding your own GFM Preview, or implementing a system by which we can do it ourselves would be golden for me- and I'm sure the majority of your users would appreciate some kind of Markdown preview style.