new block: progressbar

![2014-12-02_1609](https://cloud.githubusercontent.com/assets/1333220/5263031/9ae9b42e-7a3d-11e4-9a1a-76abcf21cc69.png)

:+1: to @dfilatov 

How all this `__text` staff could be used with "islands" theme? How about moving it to the "design" level?