Add Sizing page

Hey @iuloshi, do you mind reviewing this today? I need to add a sizing page that I can reference for the Kickstarter backers to use to pick their shirt sizes. This doesn't have to be referenced in the main nav, as folks not associated with the Kickstarter wont really need it (yet).

I'll be adding a bit more content, but wanted to get the initial page up incase you had any structural things you wanted to tackle on it! Thanks!!

![screen shot 2014-09-03 at 4 56 08 pm](https://cloud.githubusercontent.com/assets/1689222/4141333/2a0688d0-33ad-11e4-98d8-45e3e68e7b0c.png)