switch from WebKitCSSMatrix to a pure JS impl.

Currently tboard doesn't run at all on Mozilla Firefox -- one reason is that there's no 4x4 matrix implementation exposed to JavaScript in Firefox, so I'm switching to FirminCSSMatrix which runs in JavaScript everywhere.
Attempt to query property and event names for cross-browser compatibility
Use textContent instead of innerText
Works on Firefox except for the wave animation on draggable letters