Updating README.md with information on how to set up a Linux development environment
Cleaning up the implementation of the compass

We were using a tilt compensated eCompass algorithm but it isn't robust
enough as it accumulates error, we now are just using the magnetometer
data. If we want more orientation information we should use a more
robust approach to sensor fusion like Madwik's algorithm or Mahony's
(some files were here for that, but they were not as clean as the
 implementations found here
 http://www.x-io.co.uk/open-source-imu-and-ahrs-algorithms/)
Merge branch 'LinuxDev'

Updating README.md to include documentation for development on Linux