added usage in comment

diff --git a/mp3tohtml.py b/mp3tohtml.py
index c4432f0..0dcfaf7 100755 (executable)
--- a/mp3tohtml.py
+++ b/mp3tohtml.py
@@ -1,5 +1,7 @@
 #!/usr/bin/python
 
+# mp3tohtml.py <mp3_dir>
+
 import glob
 import sys
 import eyeD3