vnu 20141013 (new formula)

Not 100% sure I did this correctly, but I based it on [`htmlcompressor.rb`](https://github.com/Homebrew/homebrew/blob/master/Library/Formula/htmlcompressor.rb) and it's working for me. 

- I used an explicit `version` because ".jar" was getting tacked onto the end by Homebrew
- I used the `.jar` file instead of building from source because [the build process involves downloading 300MB of dependencies](https://github.com/validator/validator#build-instructions).
Use system instead (if there's no output) which will check the error code.