rails4: gemify simply_versioned

closes CNVS-14287

test plan: versions should work same as before. for instance, wiki page
versions and quiz versions.

Change-Id: Ibbf9dd9787711c9d6d08f40add6378a906fde968
Reviewed-on: https://gerrit.instructure.com/41243
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>