Khan/khan-exercises — pull request #37157 by peterolson (2013-01-08 20:46:33+00:00)
Title: Added number sets excercise per card 472 on the Trello board.

I added a number sets excercise, per this request on Trello:
https://trello.com/card/number-sets/4d87e664967a0775082939ab/472

This is my first excercise (as well as my first pull request) so let me know if I need to do something differently.