Expose updated versions as a report

My company tasked me with creating a report that summarizes the available updates to a given project's dependencies. As I was doing my research, I realized that it might be a good addition to the versions-maven-plugin.

One of the main use cases we envision is an assembler assessing the state of his dependency tree just before a release, looking for updated versions to pull in. Having this information available in a report makes it easily available to others, even those who might not have Maven installed. As a side benefit, it would also allow them to prove due diligence after the fact, i.e. that they took all updates available at the time (or consciously chose to ignore them).

I've already got all the code written, and will upload it momentarily.