Add ability for changes-check to validate that the changes.xml release date is the day of the release

I like the functionality included in the changes-check in MCHANGES-140. It would be nice, in addition to checking the format of the date, if an option could be added to have it check to see if the date of the release in the changes.xml is the current date when the goal is run. I would like to be able to have release:prepare or release:perform fail if the changes.xml did not have the right day. This definitely should be an option that is off by default.