Update README with --track-gain argument

README.md

@@ -8,7 +8,9 @@ Forked from the [shuffle-db-ng project](https://code.google.com/p/shuffle-db-ng/
 Just put your audio files into the mass storage of your IPod and shuffle.py will do the rest
 ```bash
 $ python shuffle.py -h
-usage: shuffle.py [-h] [--disable-voiceover] [--rename-unicode] path
+usage: shuffle.py [-h] [--disable-voiceover] [--rename-unicode]
+                  [--track-gain TRACK_GAIN]
+                  path
 
 positional arguments:
   path
@@ -18,6 +20,10 @@ optional arguments:
   --disable-voiceover   Disable Voiceover Feature
   --rename-unicode      Rename Files Causing Unicode Errors, will do minimal
                         required renaming
+  --track-gain TRACK_GAIN
+                        Store this (nonnegative integer) volume gain for all
+                        tracks; 0 (default) means no gain and is usually fine;
+                        e.g. 60 is very loud even on minimal player volume
 ```
 
 #### Additions to the original