Fix issue #29: missing Beautifulsoup Python dependency

This adds the missing `run_depend` on `python-beautifulsoup` to `package.xml` of `ur_driver`.

Also adds `run_depend` on `trajectory_msgs`, as that was missing as well.

TODO: I'm not sure the `build_depend` tags are supposed to be there. [Python module dependencies](http://docs.ros.org/groovy/api/catkin/html/howto/python_module_dependencies.html) only talks about `run_depend`. 

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First reviewed pull-request? @sedwards?