Fix #1493

https://github.com/ivaynberg/select2/issues/1493 where select2 with an `<input>` (single string, not tags) does not have its search field initialized with the text value.  Initializing this allows users to edit their selection and perhaps create a new entry via createSearchChoice.

EDIT: getting back the behavior from 1.0 would be fine for me, at least. See http://ivaynberg.github.io/select2/select2-1.0.html under "Loading Data".  This behavior has not worked since then.