Adds servo write changes for new spark core default firmware update.
Remove commented line
Fix tests and update servoWrite value from 0-255 to 0-180
Fix test to pass with new servo implementation.
Merge pull request #16 from hybridgroup/add-servo-write

Add servo write
Bump version to 0.13.1
Merge pull request #17 from hybridgroup/dev

Bump version to 0.13.1