Fix issue 740
Added test for logging other sessions out
Added note about clear_user_sessions being dependent on SESSION_ENGINE
Merge pull request #99 from Aaron1011/master

Closes: http://openhatch.org/bugs/issue740

Thanks so much for these changes! This is super high quality code, and I'd love if you'd be willing to review others' pull requests to give them feedback so they can write as great code as you did!

Pardon the delay, and I hope to see you on IRC again soon!