airblade/paper_trail — pull request #280 by TylerRick (2013-10-02 22:23:56+00:00)
Title: Don't try to write timestamp attributes just because the method exists; only write it if it is a real attribute.

This resolves this error you would get if you defined a created_on method (virtual attribute) in
your model, for example:

DEPRECATION WARNING: You're trying to create an attribute `created_on'. Writing arbitrary
attributes on a model is deprecated. Please just use `attr_writer` etc.