Fix copying files to build/npm-react recursively

The intention of the `npm-react/**/*` rule was to copy recursively but it would have flattened any nested directory structure. I changed the `build/modules` rule to copy recursively as well, which is necessary for `ReactTestUtils` to be able to require `test/mock-modules.js` successfully. (`ReactTestUtils` isn't included in a clean `npm-react` build currently but it will be in the future.)

This also makes running ART tests more practical.
Remove unused grunt jsx config options

Since 5466d0a06382892106da7e237f3330b43a60cc95, the `__DEV__` isn't used any more. I can't find anything that uses the `debug` flag either.
Merge pull request #921 from spicyj/grunt-jsx-no-dev

Remove unused grunt jsx config options
Merge pull request #918 from spicyj/npm-react-rec

Fix copying files to build/npm-react recursively
Change ReactPropTypes invariant's to console.warn.
Perf Test for the propTypes change.