#2290 - changed text to label for TOS checkbox
some changes to left nav to be more accessible
Merge branch 'master' of https://github.com/Stanford-Online/class2go into giulio-tpg-report-2290
made announcement expand/collapse UI much more user friendly
add hidden descriptor to dropdown menus to inform keyboard navigators of dropdownn status
enabled tab selection on left nav headings but added link following prevention
added accessible features to left nav
reordered html order of arrow/save/submit buttons for accessible logic
added quiz attempts hidden-accessible informational span
cleaned up code to be more elegant
merged master into this branch
beginning to incorporate TPG person's comments
better voiceover behavior, fixing the last beastly accessiblity issue
Merge pull request #2404 from Stanford-Online/giulio-tpg-report-2290

Fixes beastly accessibility bug we had! (closes #2290)