Merge pull request jarektkaczyk#22 from crlcu/master

Fix the way join keys are set for a relation that's instance of HasManyThrough

src/Relations/Joiner.php

@@ -204,7 +204,7 @@ protected function getJoinKeys(Relation $relation)
         if ($relation instanceof HasManyThrough) {
             $fk = $relation->getQualifiedFarKeyName();
 
-            return [$fk, $relation->getParent()->getQualifiedKeyName()];
+            return [$fk, $relation->getQualifiedParentKeyName()];
         }
     }
 }