tiny mce toobar now responsive

fixes CNVS-4660

test plan:
  - go to the places with tiny MCE
    - text submissions
    - quiz questions
    - calendar events
    - syllabus
    - outcomes
    - wiki page edit
    - discussions
    - profiles(?)
  - make sure it looks okay & resizes well

Change-Id: Ifd6406a0b738c43ed890d18ca3347ff2dc529bf0
Reviewed-on: https://gerrit.instructure.com/34583
Reviewed-by: Cameron Sutter <csutter@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Hilary Scharton <hilary@instructure.com>