Merge branch '16-add-volume_set-event-type' into 'master'

Resolve "Add "volume_set" event type"

Closes #16

See merge request !13

addon.xml

 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <addon id="script.spotify.screensaver"
     name="Spotify Screensaver"
-    version="0.0.9"
+    version="0.0.10"
     provider-name="Benoît Harrault">
     <requires>
         <import addon="xbmc.python" version="2.25.0"/>

gui.py

@@ -129,9 +129,18 @@ class GUI(xbmcgui.WindowXMLDialog):
         ):
             self._remove_images()
             self.next = True
+        elif event_type == 'volume_set':
+            self._unimplemented_event_type(event_type, event_value)
         else:
             self.log('unknown event type: ' + event_type, xbmc.LOGERROR)
 
+    def _unimplemented_event_type(self, event_type, event_value):
+        self.log(
+            'unimplemented event type: ' + str(event_type)
+            + ' (value: ' + str(event_value) + ')',
+            xbmc.LOGDEBUG
+        )
+
     def _preload_images(self, track_id):
         self.log('preload images for track: ' + track_id, xbmc.LOGERROR)
         self._get_track_data(track_id)