Added static assets for displaying an AJAX loading page.

This fixes issue #2, adding a loading page. This page uses AJAX to check if the instance has initialized yet and if so, reloads the page. If an error occurs, it is displayed on the page.

Note: I wasn't sure if the response from the server was literally the text "true" or if the response was wrapped in JSON, so I assumed the former. I can easily make the necessary changes if this is not the case. If the server responds with a 500 status code, the response body is displayed on the page.