Correctly use the .py name for the DMX mixer

dmx/launchd/com.uberzach.ola.dmx.plist

@@ -22,7 +22,7 @@
 	</dict>
 	<key>ProgramArguments</key>
 	<array>
-		<string>/Users/tv/bin/video/dmx/dmx.pl</string>
+		<string>/Users/tv/bin/video/dmx/dmx.py</string>
 	</array>
 </dict>
 </plist>