Two important changes

  - Added Simpson rule integration for the gyro.  This calculation
    should provide a slight improvement over the trap z integration
    I was previously running.  This effectively allows me to run
    a filter over four steps of data.
  - I corrected errrors in the PI controller to that were eliminating
    the input from the I component.  I also changed the PI controller
    to accept both standard and parallel forms of the equation, with
    the system now configured to run on the standard form.