making small UI revisions:
* removing unused icons
* adjusting spacing on response buttons/tips for smaller viewports
* revising step status width/size
moving LMS overrides completely to _shame.scss
revising styling/layout for error messages
moving more LMS override styles over to _shame.scss
syncing up step__actions simplification
Merge pull request #144 from edx/talbs/fix-uimisc

Fix - General UI/Front End Clean Up