[aurorae] Connect PlastikButton to options::colorChanged signal

Fixes incorrect button color. DecorationOptions and PlastikButton are
both connected to decoration.active and the button gets invoked first,
thus the titleBarColor is still for the previous state. This was fun!

clients/aurorae/themes/plastik/package/contents/ui/PlastikButton.qml

@@ -158,4 +158,8 @@ DecorationButton {
             }
         }
     }
+    Connections {
+        target: options
+        onColorsChanged: button.colorize();
+    }
 }