Debian package python-bloom should specify the correct version of dependencies

Installing or updating python-bloom on Ubuntu will not update its dependencies correctly. E.g. after updating, it throws the error `pkg_resources.DistributionNotFound: catkin-pkg>=0.1.10` 

By explicitly stating the version of the ependencies python-catkin-pkg, python-rospkg, python-rosdep, and python-vcstools in the .deb they would automatically get pulled in after an update.