Add steps for release to HOWTO

Include reference to [local prelease](http://wiki.ros.org/regression_tests#How_do_I_setup_my_system_to_run_a_prerelease.3F), [release new package version](http://wiki.ros.org/bloom/Tutorials/ReleaseCatkinPackage), and [releasing for a new ROS distro.](http://wiki.ros.org/bloom/Tutorials/ReleasingForANewROSDistro)