Merge commit '8a9f2f8a0a7683fa0bad8bf33f209cb915e2ce3c'
Update to clojure 1.4
Switch to refheap for pasting.
Try to recover from OOM issues
Whole buncha new stuff.
Put session data in mongodb
Fix problem submission, static URLs, invalid dependencies
- Autodetect mobile browsers
- Prettify codebox
- Start improving test coverage
- Some basic validation of user email addresses
- AJAX auto-updating of "N problems solved and counting"