Improved compatibility with PaperTrail

This is my attempt to fix airblade/paper_trail#203.  According to what @floehopper has said in the comments of his pull request, I think this should probably do the trick.  I don't have a ton of experience using the Globalize3 gem, so if someone could proof this, and / or provide a failing test for the scenario he is referencing, that would probably be better than just merging this in.  That being said, this shouldn't break any functionality, and all tests still pass with this implementation.