Merge branch 'master' of https://github.com/worklist/hifi into gyroquat
Use quaternions for rotation estimates.
Enhanced workiness.
Acceleration is presumably relative to the current orientation.
Add back yaw decay the quaternion way.
Coordinate fix.
More compiley.
Approach the "down" direction more rapidly.
Merge branch 'master' of https://github.com/worklist/hifi into gyroquat
Merge pull request #499 from ey6es/gyroquat

Converted gyro rotation computations to use quaternions, fixed coordinates and increased rate of convergence to current gravity.