Merge pull request #1189 from nowackipawel/patch-3

$myModel->find(string "value-of-my-primary-key") #1188

system/Model.php

@@ -326,7 +326,7 @@ public function find($id = null)
 					->get();
 			$row = $row->getResult($this->tempReturnType);
 		}
-		elseif (is_numeric($id))
+		elseif (is_numeric($id) || is_string($id))
 		{
 			$row = $builder->where($this->table.'.'.$this->primaryKey, $id)
 					->get();