[modules/cmus] Make displayed string configurable

Allow the user to use all tags read by cmus (cmus-remote -Q|grep ^tag)
as part of the displayed data (plus the special 'tags' "duration" and
"position").

bumblebee/util.py

@@ -6,3 +6,10 @@ def bytefmt(num):
         num /= 1024.0
     return "{:05.2f%}{}GiB".format(num)
 
+def durationfmt(duration):
+    minutes, seconds = divmod(duration, 60)
+    hours, minutes = divmod(minutes, 60)
+    res = "{:02d}:{:02d}".format(minutes, seconds)
+    if hours > 0: res = "{:02d}:{}".format(hours, res)
+
+    return res