updating p5 + p5sound, adding landscape + water, and some reorganizing

I was working out of gradientstars.js.

- drawLandscape() draws a landscape out of the waveform
- created a lerpGrad() function for lerping between two colors
- renamed setGradient to rectGradient() because it makes a rectangle (or whatever shape we want!)
- took all the background color gradient stuff out of the draw loop because it wasn't being used, gave it a function setColors() in case we want to use it later