visualization tools

[plusk01]

Cleaned up the magnetometer visualization code. Renamed viz_mag to viz and folded in a republisher from rosflight_msgs/Attitude to geometry_msgs/PoseStamped so the attitude can be viewed in rviz.

The fact that the attitude portion of the viz is merely a republisher for mismatching message types makes me wonder if rosflight_io should be publishing on the tf tree? (see #33) Or maybe you don't think this viz code belongs in this repo? Visualization of attitude just seems like a natural thing to do to test ROSflight out-of-the-box.

[superjax]

Thanks @plusk01, there was some old code in there. I like your addition

I think it would be a good idea to publish to tf, though I have never done it. I'll update #33 and see if I or someone else has time to make that happen!