Add a form to start a new build

![screenshot_112613_100938_am](https://f.cloud.github.com/assets/21165/1624642/d91c7af2-56c5-11e3-8712-0bbae288c2ad.jpg)

What the title says: some times you just need to start a build without going through a hook, Fixes #26.

# To Do
- [x] handle empty form submission