added a revised network bar - hgnav


hgnav() is the macro that creates the revised network bar. It is optional; hence does not disrupt sites using the older network bar.

Sample Usage:

```jinja
{% block headerbox -%}
  <link href="//maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css" rel="stylesheet">
  {%macro site_title()%}
  	<h1 style='margin-top: 2px'>Funnel</h1>
  {%endmacro%}
  {%macro site_nav()%}
    <li><a href="">Construkt</a></li>
  {%endmacro%}
  {{hgnav(site_title=site_title(), site_nav=site_nav())}}
{%- endblock %}
```