Revert `morf.js` and `morf.noshifty.js` to their original states.

 * Added `morf.xplatform.js` and `morf.xplatform.noshifty.js` for the
new cross-platform builds.
 * Reverted `demo.html` to its original state
 * Created `demo-xplatform.html` to use the cross-platform builds.
 * Use `Morf.Matrix` in lieu of `WebKitCSSMatrix` or `XCSSMatrix`
 * Created `Morf.prefix` based on static values if `Modernizr` is missing.