Merge pull request #9 from asr1/master

oi, ir, and sonar functionality
Merge pull request #10 from dwtj/master

send_mesg_test_mode()
`watchman` has been disabled. The start/stop watch calls have been
removed from the subsystem commands.
Merge branch 'master' of https://github.com/aore/mars-rover
Got rid of rover_calibrate
Added initial stubs and documentation to the new `sensors.py` file.
Merge pull request #12 from dwtj/master

Added initial stubs and documentation to the new `sensors.py` file.
slight reformatting
Added least squares polynomial regression code to `sensors.py`.
Added readings() functions to ir and sonar
Updated comments
Implemented `calibrate_dist()` in `sensors.py`.
Merge pull request #18 from aore/master

Merged `ir.readings()` implementation
Revised some comments and removed `_use_calibration_data()`.
Tracking down bugs the logic to get distance readings.
Removed references to calibration from the message protocol.
Fixed some command handlers, and added logic to enqueue
parts of the response message as we go deeper into the
handler functions.
Still tracking down bugs preventing control from getting readings
from rover.
Fixed bugs associated with distance readings and the
`sensors.calibrate_dist()` function.
Merge branch 'master' of https://github.com/dwtj/mars-rover into dwtj-master

Conflicts:
	rover/src/lcd.c
	rover/src/servo.c