remove previous timeline on subsequent loads
remove previous timeline on subsequent loads

ffxsam/wavesurfer.js,katspaugh/wavesurfer.js,ale-grosselle/wavesurfer.js,ffxsam/wavesurfer.js,katspaugh/wavesurfer.js,agamemnus/wavesurfer.js,agamemnus/wavesurfer.js,ale-grosselle/wavesurfer.js