Merge pull request #9 from asr1/master

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

send_mesg_test_mode()
Merge branch 'master' of https://github.com/aore/mars-rover
Got rid of rover_calibrate
Merge pull request #12 from dwtj/master

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

Merged `ir.readings()` implementation