Make it possible to pass arguments to the typeahead library

This little change allows us to pass arguments to the typeahead lib. For example, here is how you config Bootstrap 3 Typeahead (https://github.com/bassjobsen/Bootstrap-3-Typeahead):

```javascript
$("input").tagsinput({
    freeInput: false,
    typeahead: {
      source: ["foo", "bar"],
      items: 10,
      showHintOnFocus: true,
      minLength: 0
    }
  })
```