Added support in SilenceableWaveFile for skipping initial play

Ignore-this: ce65a10b997096b0987b708c35c2a312

darcs-hash:20091023170624-1e3d8-e0b59348e418076f98ccd400963c88f1b7c47d90
Added pre-generated tone WAVs

Ignore-this: 678f6b0d300c45593d17de72424c97a3

darcs-hash:20091023172318-1e3d8-598522b379998f15eebb4b74133682e38e4b6e2a