Don't include *-coverage.js files in release builds

[derek]

Is there a reason we're including the coverage files in the release/CDN builds? For example, http://yui.yahooapis.com/3.10.0/build/yui/yui-coverage.js

yui3:master $ find ./release/3.11.0pre/cdn/build/ -name *-coverage.js | wc -l
     345

Also, inclusion of these files accounts for 47% of the build directory's 34M size.

yui3:master $ du -sh release/3.11.0pre/cdn/build/
 34M    release/3.11.0pre/cdn/build/
yui3:master $ find ./release/3.11.0pre/cdn/build -name *-coverage.js  -exec du -ch {} + | tail -n 1
 16M     total

If there isn't a reason to include the coverage files, we should block them from being copied over during grunt release.

[caridy]

Aside from the regular use case (generating coverage info while testing), @davglass has this idea in mind to use the coverage version to do dynamic analysis on webapps, something like: run your app with filter=coverage and collect some information about how much of the library is the app really using, the results will be surprising for sure. In most cases, you're really only using a very very tiny % of the library. I think that will be a valid case if we can put in place the pieces to provide the proper report.