Update insertion of users to match new Klout API

* Add column 'kid' to store unique klout id associated with a twitter handle
* Replace the 1 apiv1 call to 2 apiv2 calls (1 to fetch klout id, 1 for score)
* Add "insert" code in another file, model.php so the same code can be used for submit.php & import.php (with the addition of the extra API call to fetch klout id, we better store the klout id; it's better that we fetch the klout id right away, upon inserting the user - whether over submit.php or import.php)