Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/laravel/framework/src/Illuminate/Auth/GuardHelpers.php

@@ -40,6 +40,16 @@ trait GuardHelpers
         throw new AuthenticationException;
     }
 
+    /**
+     * Determine if the guard has a user instance.
+     *
+     * @return bool
+     */
+    public function hasUser()
+    {
+        return ! is_null($this->user);
+    }
+
     /**
      * Determine if the current user is authenticated.
      *