Erase the content of the field if only the dial code is filled.
If the dial code has been selected and no number has been entered the content of the field is erased when it looses the focus.
When it gains the focus it is entered again. This avoid sending to the server a parameter with only the dial code entered.
Issue: The onkeyup event should not be triggered during init.
	- Replace the content of telInput.keyup with the call of a new internal method called _performKeyUpAction.
	- instead of triggering the key up event call _performKeyUpAction.

Issue: the keyup event should be triggered when a new country is changed.
	- trigger on keyup when selecting a new flag

New public function added: val
	- this function allows to programmatically set the value of the phone number and update the flag at the same time.
tidy up and optimisations
abstracted a couple of functions
updated minified version