Changelog

===== Turtlebot 2 =====

To make it easy for others to follow, this covers the sweeping changes made while getting 
ready for turtlebot2.

- Platform: using roslaunch argument 'base' to customise what gets launched for which platform.
  - This indirectly can be set via the TURTLEBOT_BASE environment variable.
- Zeroconf: for advertising the ros master.