fix(typeahead): incompatibility with ng-focus

Used timeout to avoid $rootScope:inprog error

Fixes #1773
Closes #1793
chore(typeahead): fix typo in comment

Closes #1925
fix(carousel): correct glyphicon

Fixes #2006
Closes #2014
chore(dropdown): remove unused var
Closes #2023
feat(button): allow uncheckable radio button

Acts as a hybrid checkbox/radio-button, selecting exclusively among the button set, but also allowing the selected item to be unselected, leaving the button set without a selected item.

Closes #1760
feat(typeahead): add `aria-owns` & `aria-activedescendant` roles
fix(dropdown): do not call `on-toggle` initially

Closes #2021
fix(modal): give a reason of rejection when escape key pressed

Fixes #1956
Closes #1991
docs(typeahead): add `typeahead-on-select` callback parameters

Closes #2047
feat(datepicker): make widget accessible

 * keyboard navigation
 * WAI-ARIA roles
 * popup will close on escape on input or calendar
 * handle focus when closing popup

BREAKING CHANGES: popup calendar does not open on input focus