wrap long titles on assignment show page

fixes CNVS-13555

test plan:
- create assignments with very long titles both with and without spaces
- they should look okay on the assignment show page

Change-Id: Ia558c9f43e55ea5cf544716b0840ceceb964998f
Reviewed-on: https://gerrit.instructure.com/36660
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cameron Sutter <csutter@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>