Minor template enhancement (#79)

* Added template block for cookie and terms-and-conditions storage

* More minor doc tweaks

Author: delsim

demo/demo/templates/base.html

@@ -40,6 +40,7 @@
      </nav>
    </header>
    <main>
+     {% block main_top%}{% endblock%}
      <div class="container">
        {% block content%}{% endblock%}
      </div>

docs/template_tags.rst

@@ -77,8 +77,8 @@ The ``plotly_header`` and ``plotly_footer`` template tags
 ---------------------------------------------------------
 
 ``DjangoDash`` allows you to inject directly the html generated by ``Dash`` in
-the DOM of the page without wrapping it in an iframe. To include your app CSS and JS, you have
-to include two tags in your template, namely ``plotly_header`` and ``plotly_footer``, as
+the DOM of the page without wrapping it in an iframe. To include the app CSS and JS, two tags
+should be included in the template, namely ``plotly_header`` and ``plotly_footer``, as
 follows:
 
 .. code-block:: jinja
@@ -103,7 +103,8 @@ follows:
     </html>
 
 This part in mandatory if you want to use the :ref:`plotly_direct <plotly_direct>` tag, and these two tags can safely be included
-on any page that has loaded the ``plotly_dash`` template tag library with minimal overhead. Neither tag has
+on any page that has loaded the ``plotly_dash`` template tag library with minimal overhead, making them
+suitable for inclusion in a base template. Neither tag has
 any arguments.
 
 Note that if you are using any functionality that needs the use of these tags, then the associated middleware