first audio number works

extremely slow trigger.
fade-in works

1000ms duration hard-coded for now. May need flexibility to vary with
audio clip duration.
fade in duration parameterised

also tested (and failed) for 2y/o. Needs to snap on and play audio
instantaneously.
deleted unused files

old test audio and image folder
wav file replacement

funny squeals happen
Merge pull request #1 from Cheddles/audio

Audio