Merge pull request #1 from ckruse/emscripten

moving interface code to header file (where it belongs)
adding sass.js and sass.worker.js for simpler integration. adding filesystem access.
adding transparent sub-directory support to writeFile()
fixing callbacks for worker api
Merge remote-tracking branch 'rod/emscripten' into emscripten

Conflicts:
	js/console.html
	js/libsass.worker.js
	js/worker.html