Uses ejs for templating.

EJS is a popular templating system for node (see https://github.com/tj/ejs). This uses Koa's wrapper for it (see https://github.com/koajs/ejs).

Public files are now just served from the root path of the URL (`http://localhost:8080/css/main.css`, for example) but are still stored in the public directory.

To check this pull request out, you could use `hub` from Github: https://hub.github.com/ and run `git checkout PULLREQUESTURL`