rqt_bag does not position icons correctly on OS X

![Screen Shot 2013-04-04 at 1 44 14 PM](https://f.cloud.github.com/assets/100427/341188/c437518c-9d68-11e2-92c3-658b4397f04a.png)

See answers.ros.org post here:

http://answers.ros.org/question/60017/rqt-not-showing-icons-in-osx/