Improve viewer demo

[qwofford]

I am testing the simple viewer at <ROOT>/dsi/viewer and I'm finding that it does not work for me. Can we either include a README.rst that says how to use this or remove it from the project?

[jpulidojr]

I can properly document this viewer with proper readme (need to enable use of javascript offline in browser settings, or set up small http server to serve/run the code). With the current refactor in #18 , the 'viewers' folder is gone along with references to the Cinema viewer