add epic editor

https://github.com/OscarGodson/EpicEditor
http://oscargodson.github.com/EpicEditor/

EpicEditor is an embeddable JavaScript Markdown editor with split fullscreen editing, live previewing, automatic draft saving, offline support, and more. For developers, it offers a robust API, can be easily themed, and allows you to swap out the bundled Markdown parser with anything you throw at it.