Added code parsing input generating an input map stored as the variable
input_map_ in us_driver.cpp. Also added code for checking acknowledgement
from uC. Still has issues when acknowledgment is not properly received.
UARTDriver should flush before being used.
Resolving merge conflict.
Conflict resolve attempt 2.
Merge branch 'us_driver'
Used a global constant for defining maximum number os sensors.
Added function to generate ExRangeArray. Only generates a value if a
reading from the corresponding sensor is found. Have written the code
for both direct and indirect sensing however have not been able to check
	code for indirect sensing.
Now publishing ExRangeArray messages.
Resolved a mistake.
Frame ids in ExRange messages.
us_driver will now differenciate between just a pinging sensor and a pinging and listening sensor.
Changed topic of ExRangeArray from msg_array to us_reading.
Added some details about pin mappings.
Added a check that a maximum of 16 timer values are taken. This prevents corruption of sensor address value.
Now selects the first listening sensor value which produces a positive difference with the pinging sensor base value.
Merge git://github.com/alishuja/ipa_lcrob
added light