Remove some cruft in mpd module

i3pystatus/mpd.py

@@ -40,7 +40,6 @@ class MPD(IntervalModule):
     port = 6600
     s = None
     format = "{title} {status}"
-    format_sparse = None
     status = {
         "pause": "▷",
         "play": "▶",
@@ -48,7 +47,6 @@ class MPD(IntervalModule):
     }
     color = "#FFFFFF"
 
-    vol = 100
 
     def _mpd_command(self, sock, command):
         try:
@@ -68,10 +66,6 @@ class MPD(IntervalModule):
         except Exception as e:
             return None
 
-    def init(self):
-        if not self.format_sparse:
-            self.format_sparse = self.format
-
     def run(self):
         try:
             status = self._mpd_command(self.s, "status")