Remove unused Ticker

Both the accelerometer and magnetometer class had Ticker members that
weren't being used so I removed them.
Add ITG-3200 gyro support

This commit adds support for the InvenSense ITG-3200 gyroscope.

I also updated the Processing samples to accept the 3 additional gyro
reading fields at the end of the CSV line and removed an old debugging
check which was searching for errant accelerometer values.