Let the statisticsForms model return the total signups instead of the form model

- added unit test for getTotalSignups() method

lib/Models/Form.php

@@ -39,11 +39,6 @@ class Form extends Model {
     return parent::save();
   }
 
-  function withSignups() {
-    $this->signups = StatisticsForms::where('form_id', $this->id)->count();
-    return $this;
-  }
-
   static function search($orm, $search = '') {
     return $orm->whereLike('name', '%'.$search.'%');
   }