Use Eggshell npm module, remove unnecessary scss from repo.

Moved the client-side to use the Eggshell npm module so we can remove a bunch of the files in `/src/scss`. All the files in `/default` and `/common` have been removed. A few additions were made to the `/partials` and `style.scss` file to compensate for a few missing properties. Also hackishly styled the login page.

/cc @hunvreus @kuno