Adding wavesurfer.js

Navigable waveform using WebAudio and Canvas.

Source: https://github.com/katspaugh/wavesurfer.js

License: Creative Commons Attribution 3.0 Unported License

Original contributor: Alex Khokhulin https://github.com/xoxulin who can be contacted at alex.hohulin@gmail.com. I did not add him as the author in this package.json because in his own github repo he also left it out. Perhaps because this seems like he would have taken more credit if he added his name there. This is implied by his link to “the awesome contributors!" which links to https://github.com/katspaugh/wavesurfer.js