Display featured ``Posts`` in the blog section.
Add advertising box in the homepage.
Replace ``advertising`` with ``snippets``.

Snippets is a better wording and reflects what the
django app do: Place snippets of content on specific
areas of the site.

These ``Snippets`` can have different content and design.

They are embeded by using a ``snippet`` template tag::

    {% snippets KEY TEMPLATE_PATH %}

Where:
 - ``KEY`` is the slug of the ``Snippet``
 - ``TEMPLATE_PATH`` is the path to the template to be rendered.
Bugfix: Make sure the ``context`` is not overriden.

The variable name for the string template context was removing
the actual ``context`` of the tempalte where the tag was
embeded.
Update template tag to embed featured snippet in the ``blog``.