Maint/1.2rc/restore changelog

This PR returns the CHANGELOG to Puppet Dashboard, reverting the commit in which it was removed, as it was missed by some for its easy display of change set difference. It was originally removed with the goal of simplifying the release process by removing a manual step and under the assumption no one found it useful (turns out I was incorrect). However, in the spirit of removing manual processes, this PR removes the VERSION file instead, and updates the version link to parse CHANGELOG. It maintains the original behavior of pointing to the CHANGELOG file on github.