Publish bumpers data (if available)

[reed-adept]

Copy and paste from rosaria is fine, unless someone is inspired to do some more heavy duty refactoring (if so please discuss on user list)

[RobertBlakeAnderson]

We were just discussing adding this to our fork the other day. I'd like to do it a little differently than rosaria. Rosaria publishes the bumper state on every call to the publish() function. To save bandwidth, I'd like to only publish when an event occurs. The Kobuki API provides an example of this: http://docs.ros.org/hydro/api/kobuki_msgs/html/msg/BumperEvent.html

[reed-adept]

Sounds good. I guess you can just save the bitmask and publish it (and save) if it changes, there's no event driven trigger or callback for that in ARIA. (It just provides the bumpers state every cycle (100ms) as a bitmask) [Aria also has the ArRangeDevice point cloud interface for it as well, creating a point whenever a triggered bumper is seen, not sure if anyone would find that useful?]

[RobertBlakeAnderson]

Added bumper publishing to PR #19 .

[reed-adept]

Merge request #19 includes battery information. It has now been merged into master. Anyone interested can take a look and let us know if this will be ok.