Larger clickable area for checkboxes on the retries page

### Before
![screenshot 2013-11-20 10 53 11](https://f.cloud.github.com/assets/167215/1579201/689e8cb2-5192-11e3-834c-6c0c7aee0a45.png)

### After
![screenshot 2013-11-20 11 15 10](https://f.cloud.github.com/assets/167215/1579202/689eb87c-5192-11e3-8c74-fa0333b7617f.png)