Add 12 hour support, immediate set, input change

Add 12 hour AM/PM support, using options based on timeentry by @kbwood (https://github.com/kbwood/timeentry).

Add new option immediateset that sets input as soon as clock time changes. Factor out setting input into new setInput() function.

Also track input change with new event handler inputChange. Factor out setting time from input into new getInput() function.