The & character in class title causes tweets to be cut off

When the & character is in a session title in the calendar it causes tweets to be cut off where the & occurs.

Example: https://twitter.com/#!/ubuntuclassroom/status/90478186516852736

We've been working around this bug by not including it in session titles, but with so many people having access to editing the calendar without review this has gotten trickier to control, so we should probably see if it's fixable in the code.