Scientific notation support for onMath

The number regex now consumes entire numbers at once, including ones using scientific notation (e.g. 3e12) which were previously not recognized.

![screenshot 2014-06-24 at 5 34 46 pm](https://cloud.githubusercontent.com/assets/990370/3378223/737b6e98-fbe7-11e3-9386-38dec127777e.png)