Correct the construction of the refname

The refName that is generated for the RefUpdated event
for tags contains the prefix "refs/tags" unlike other
RefUpdated events.

This attempts to ensure that the correct RefName is always
produced.
Merge pull request #27 from scoheb/correct-refname

Correct the construction of the refname
Updated changelog
[maven-release-plugin] prepare release gerrit-events-2.4.2
[maven-release-plugin] prepare for next development iteration