Fix #6 adds :previousFrame as a texture input.  Need to add a good example usage.  Works pretty well.
Add zoomwave example to 00demo (forgot to add with this checkin, will do next) to show off the :previous-frame feature.

Change from camel case to hyphen for :overtone-audio and :previous-frame keywords.

Clarify some examples that don't use :overtone-audio texture.
add zoomwave example to show off the :previous-frame texture feature.