Gyroscope Constructor

Similar structure to accelerometer

Angle integration returns a single number per axis, not a stream.
add documentation for gyro

Also make johnny-five.js aware of Gyroscope constructor
Style nits

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
v0.6.16

- Gyroscope class

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>