Rename scripts directory, rename some paths in tasks.
Make clean task dispose project temporary (compiled) files too.
Copy index.html rather than serve it from project source.

This is not ideal, but instead of turning it a Jade template or some other
thing, like I did before with the stylesheets and LESS, better take out this
file from the project source code.

Maybe I'll fix that later.
Fix `watch` task.
Remove unused `devDependency`.