Add a description to package.json

![screen shot 2014-12-05 at 3 47 45 pm](https://cloud.githubusercontent.com/assets/2723/5325027/ee5a6684-7c96-11e4-883a-096efb77601c.png)

Didn't know what you wanted for a description so I made one up. Mostly I try to use "tidy" in at least three sentences every day.

/cc @benogle