Remove units from numbers

This is a first step to decouple formatting from information because of
two reasons:

 1. The components should only gather and return the values by design
 2. Fine grained user control should be a focus

Scaling will be implemented in a different way in a later commit.

components/volume.c

@@ -42,5 +42,5 @@ vol_perc(const char *card)
 
 	close(afd);
 
-	return bprintf("%d%%", v & 0xff);
+	return bprintf("%d", v & 0xff);
 }