add bullet_instructure gem to RAILS3

Change-Id: I3d0ae2c2d7ed9665f920d4aab79ae6837c67d32d
Reviewed-on: https://gerrit.instructure.com/36694
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Kyle Rosenbaum <kyler@instructure.com>
Product-Review: Hannah Bottalla <hannah@instructure.com>
QA-Review: Hannah Bottalla <hannah@instructure.com>
Tested-by: Hannah Bottalla <hannah@instructure.com>