Added demo
1. Added validation that reverts to last valid value when an invalid value is entered.
2. Implemented $filter for $render method.
3. Implemented ngFilter for list of selectable time.
4. Added time-format attribute which is used by $filter.
5. Updated stringToDate function to handle AM/PM properly.
6. Updated demo page.
7. Updated unit tests.
Merged development -> master

Conflicts:
	angular.timepicker.js
	demo.html