Step 1: `WebKitCSSMatrix` -> `XCSSMatrix`. Still works in Chrome/Safari.

 * Added XCSSMatrix
 * Added XCSSMatrix.ext.js instead of making it a mixin.
 * Added `modernizr.custom.js` from http://modernizr.com/download/#-cssanimations-csstransforms-csstransforms3d-prefixed-teststyles-testprop-testallprops-prefixes with the union of features required for Morf and XCSSMatrix
Step 2: Remove all WebKit-specific code. Works in Safari/Chrome/FF20+.

 * Failing in Opera 12.15
 * Create a lookup table for all prefix-able properties (`dom`, `css`, `events`).
 * Expose lookup table as `Morf.prefixed`
Committed old build files in 273b275.
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.