New Progress Bar component

New component: Progress Bar, in two different sizes.

![Large Progress Bar](https://f.cloud.github.com/assets/188748/488597/93567dc8-b982-11e2-8376-542d073f1d3e.png)

![Progress Par](https://f.cloud.github.com/assets/188748/488611/ca8ba20a-b982-11e2-89f0-d19827560b0e.png)