Quick Refactor

Removes all unneeded modules and makes required changes to work with any path. Removes "external" plugins from being included automatically. 

Updated usage example:

```html
    <script src="scripts/embed.js"></script>
    <script>
      new Notebook(document.body, {
        inject: [
          'plugins/proxy.js',
          'plugins/gist-persistence.js',
          'plugins/filter-properties.js',
          'plugins/raml-client-generator.js',
          'plugins/function-property-filter.js'
        ],
        exec: [
          'proxyPlugin.attach(App.middleware);',
          'gistPersistencePlugin.attach(App.middleware);',
          'filterPropertiesPlugin.attach(App.middleware);',
          'ramlClientGeneratorPlugin.attach(App.middleware);',
          'functionPropertyFilterPlugin.attach(App.middleware);'
        ].join('\n')
      });
    </script>
```

Includes a fix to the typo for reenabling auto resizing iframes, a fix for opening links in the parent window and a change to make the iframe contents butt up right to the edges. Also adds `PROXY_URL` environment variable for the proxy plugin.