Add note about getting Viz.js from the releases page.
Add note about getting Viz.js from the releases page.

shusenl/viz.js,mdaines/viz.js,mcanthony/viz.js,shusenl/viz.js,mcanthony/viz.js,mdaines/viz.js,shusenl/viz.js,mcanthony/viz.js,mdaines/viz.js,mdaines/viz.js