Update textinput.js - 'refresh'  method for textinput

reference to issue https://github.com/jquery/jquery-mobile/issues/5708
and previous pull request.
https://github.com/jquery/jquery-mobile/pull/5766
added 'refresh' method to textinput  

test case :http://jsbin.com/edidil/5/   [Got various  combinations of input fields and button to refresh input.]