Autocomplete dynamic lookup feature 

I have added a  very valuable feature that I borrowed idea from jQueryUI autocomplete widget.
Now, "lookup" option is able to take a function as a value for example: 

function( value, response ) {
// here goes some code and calculations

// update lookup data 
response(myAutoCompleteData);
}
as lookup function gets fired on every value change. 

This is very useful when you need to work with dynamic,live binded local autocomplete data / collections and other APIs such as Google Maps etc.. 

If you need anything else for this feature to get merged other than unit test I had added, just tell me and I'll be happy to add.
If this doesn't get merged, anyone else needing this can clone my forked repo.