hardcode example.html as body

sandboxApp.js

@@ -80,7 +80,7 @@ app.get('/examples/:slug', function(req, res) {
   const { slug } = req.params;
   const config = readConfigJson(slug);
   const { title, html, js, css, libsCss, libsJs } = config;
-  readFileAsync(__dirname + '/exemples/' + slug + '/' + html[0])
+  readFileAsync(__dirname + '/exemples/' + slug + '/example.html')
   .then(body =>
     Mustache.render(sandboxTpml, { body, slug, title, js, css, libsCss, libsJs })
   )