Update Modules Reference for Audulus 4

[markalanboyd]

http://docs.audulus.com/modules/

I will rewrite all modulation documentation for Audulus 4.

The modulation documentation is already being written as I'm creating the module library. The task here is mainly to pull that info into a Markdown document that can be put on the web.

Ideally in the future, modulation documentation will be further fleshed out with copious examples of use and example patches for each module.