Handle paper_trail's custom version classes.

[inclooder]

Fix for #303
Handle paper_trail's custom version classes.

[kerrizor]

Hi, and thanks for the PR! Apologies on not responding sooner; my workflow for being notified of new issues broke such that I received some notifications, but not all, and unfortunately yours was one I missed.

If you have the time, could you rebase and resubmit? I recently merged fixes for minitest that may help clear up your test failures.

[inclooder]

@kerrizor thank you for your time. I've rebased the branch but the master is failing so this one will fail too :(

[kerrizor]

@inclooder Hmmm.. looks like an apt-get hiccup on Travis.. I've rerun the build for and it does show green now.

[kerrizor]

@inclooder I had so many things to do with rebasing and merging that I went ahead and opened a new branch for this PR at #325 (don't worry, you'll still get credit! 😉) Thanks again for your contribution and your patience!