increase length of bong.wav so that it plays properly (see readme.md).

resources/magic/data/_excluded/sounds/readme.md

@@ -0,0 +1,13 @@
+### bong.wav
+original wav which was found not to play correctly in Linux Mint 17.3 because it was [too short](http://bugs.java.com/bugdatabase/view_bug.do?bug_id=4434125).
+
+
+#### fix: increasing length of wav (on linux)
+    # make a 1 second wav of silence.
+    ffmpeg -filter_complex aevalsrc=0 -t 1 1Sec.wav
+    
+    # concatenate the silence to the end of original sound file.
+    ffmpeg -i bong.wav -i 1Sec.wav -filter_complex '[0:0][1:0]concat=n=2:v=0:a=1[out]' -map '[out]' output.wav
+    
+    # convert to 16kHz sample.
+    avconv -i output.wav -ar 16000 new-bong.wav