Add some kind of ros test

[harlowja]

This is more of just a tracking thing (I'm not sure if this is the right area).

But travis should be ensuring that some level of 'ros_bridge' functionaltiy works on an ongoing basis (at some level of bare minimum support).

For example, from my local work it seems like libpng16 is going to break that functionality (ros packages only want to work with libpng12); so it would be great to learn about these types of issues at PR creation time instead of after merge...