Merge pull request #5 from mveldhuizen/master

Implement __isset function in Model class

src/Pinterest/Models/Model.php

@@ -88,6 +88,17 @@ public function __set($key, $value)
         }
     }
 
+    /**
+     * Check if the model's attribute is set
+     *
+     * @param $key
+     * @return bool
+     */
+    public function __isset($key)
+    {
+        return array_key_exists($key, $this->attributes);
+    }
+
     /**
      * Fill the attributes
      *