Make tag-it options all passable to the autocomplete function

[glacialspring]

This allows more control over the autocomplete action, perhaps passing {source: url} instead of {availableTags: array} (though availableTags still compatible), and can specify other options such as minLength before recognition starts.

[aehlke]

This is what I'm planning on doing, thanks, but I'd rather the autocomplete options be a nested dict inside the options, rather than passing all of our options over to autocomplete.