Sparton AHRS 8 Driver

[abrandemuehl]

We'll be incorporating the Sparton AHRS8 into our sub this year, and we need a ROS driver for it. It should publish IMU messages (http://docs.ros.org/api/sensor_msgs/html/msg/Imu.html), preferably with covariances included.

I've written this driver before, but do not have access to the code, so I can be a point of contact for advice on implementation.