Implement issue https://github.com/vanadiumlabs/arbotix_ros/issues/24:
Allow 16 bit values on arbotix_msgs/Analog messages, but assume 8 bits
by default
leng -> length
Merge pull request #25 from corot/indigo-devel

Implement issue https://github.com/vanadiumlabs/arbotix_ros/issues/24: