Fix/test build

There are 3 main changes in this patch:

* use relative path in `etc/static/head.html`, because i got `NOT_FOUND` error in file system with `file:///index.css` and `file:///index.js`, it might be occurred in other environments as well.

* `mocha.jade` should be shared here, that holds the test runtime in browser, it's just a conventional improvement.

* add should.js and sinon.js as built-in library

/cc @kenhkan