Fix style, add blankline at end of files

Author: B8Y

lib/Gitlab/Model/GroupMilestone.php

@@ -63,4 +63,4 @@ public function __construct(Group $group, $id, Client $client = null)
         $this->setData('id', $id);
         $this->setData('group', $group);
     }
-}
+}

test/Gitlab/Tests/Model/GroupMilestoneTest.php

@@ -63,4 +63,4 @@ public function testFromArray()
         $this->assertSame($data['due_date'], $groupMilestone->due_date);
         $this->assertSame($data['start_date'], $groupMilestone->start_date);
     }
-}
+}