Show only selected branch

It helps to see a specific branch like "stable".

### Screenshot

Show all branches by default.

![filter_ref_1](https://f.cloud.github.com/assets/72138/483613/c4399dbe-b8c2-11e2-844c-d3d7d46255c1.png)

Show only selected branch if checkbox is checked.

![filter_ref_2](https://f.cloud.github.com/assets/72138/483616/e059279e-b8c2-11e2-8885-54e27565b2b5.png)