update for accessibility / semantics / increase user affordance

- not allowed cursor added to restricted dates
- add restricted caption option on hover with title tag for clarity
- wheel headings are now h3 tags for semantics to relate to month/year ULs
- validation: block items (ul/li) within headerTitle to inline <span>
- <a> replaced with buttons due to lack of navigation action
- "IMH" button styling removed for base Fuel UX control
- focus on month, when showing wheel for keyboard accessibility
- focus on input on selection, when showing wheel for keyboard accessibility
- update scheduler with new markup
- do not close calendar if restricted date is clicked ("I know nothing!" says Master Sgt. Schultz)
- update index.html/index.js
new-datepicker-markup: datepicker - minor alterations
Merge pull request #599 from ExactTarget/new-datepicker-markup

update for accessibility / semantics / increase user affordance