Merge pull request #13 from Unity-Technologies/devin/pep8

AIRO-315 PEP-8ifying and cleaning up Python code

Now that our code is public it needed to be brought more in line with what python/ROS-familiar developers might expect. Updated module and class names to follow more pythonic conventions, added appropriate classes to the init file, re-structured the repository to look more like a standard catkin package, and cleaned up the CMakeList and package.xml cruft.

Tested by running through Part2 of the tutorial and seeing received messages on ROS Melodic.