Grunt should do a comparison of built directories to ensure all neccesary files are included in a release build

[derek]

release.js currently checks to ensure a select set of files are included in a release build. It should instead do a verification that everything in /build/ exists in /release/{version}/dist/. Preferably, it should also verify that the content of the files are identical, though this might be tricky since release builds are slightly different from normal builds (copyright stamp, @VERSION@ replacement in YUI.add).

This would prevent things like yui/yui3#690 and yui/yui3#704 from happening in the future.