Add turtlebot_arm repo

Sorry, I do by hand because bloom-release failed on creating the pull req:
```
Failed to open pull request: IOError - [Errno 2] No such file or directory: u'/tmp/tmpy9VVxF/https://github.com/turtlebot-release/turtlebot_arm-release.git-0.3.0-0.patch'
```
Merge pull request #5281 from corot/patch-18

Add turtlebot_arm repo