Soooort of off-topic, but I've actually had a lot of success using Cloud9 IDE (https://c9.io/) as an in-browser editor. It really closely mirrors Sublime Text 2 as far as default functionality and appearance goes. Of course, I'm coming from a Visual Studio IDE background rather than a Vim/Emacs background, so I can't vouch for its usefulness for users more accustomed to that type of work environment.
Note: not affiliated with Cloud 9