The select2 component can be configured to accept new values, as ask in Select2 dropdown but allow new values by user?
And you can see it at: http://jsfiddle.net/pHSdP/
And to be able to submit multiple new choices together with the existing ones:
select2({tags: true, selectOnBlur: true, multiple: true})
I am using Select2 4.0.3 and had to add two options:
tags: true,
selectOnBlur: true,
This worked for me
Adding attribute selectOnBlur: true,
seems to work for me.
Edit: glad it worked for you as well!