add seconds option

Adds an optional seconds dropdown in the timePicker. It would only be shown if the timePickerSeconds option is true. This was a hard requirement for me, figured I would push it up if you want to use it. Here is a JSBin before the change: http://jsbin.com/jowahawaxo/2/edit

Here is a JSBin with the new code and seconds enabled: http://jsbin.com/qiyehutana/3/edit

Here is what it looks like:
![with_seconds](https://cloud.githubusercontent.com/assets/5260472/4839006/06eba418-5ff7-11e4-949e-bcb3283f05c1.png)

And the result:
![with_seconds_result](https://cloud.githubusercontent.com/assets/5260472/4839007/0a8b05c8-5ff7-11e4-9dd8-0640198c46a4.png)