Add timepicker

This is based on bufferapp's fork applied on top of master.
It has been rewritten to display seconds instead of meridiem.

Usage example:

```js
	$('#NodeCreated').datepicker({
		showTime: true,
		autoclose: false, // when showTime is true, autoclose is ignored
		todayBtn: true,
		todayHighlight: true,
		clearBtn: true,
		format: 'yyyy-mm-dd H:i:s'
	});
```
Here's how it looks:

![screenshot from 2014-04-23 19 52 47](https://cloud.githubusercontent.com/assets/39490/2777497/3fee1de6-cae6-11e3-9785-bfc5e8fdc35d.png)