closes out tweet issues and adds inciweb narratives to details template

* adds {% empty %} template tag when no tweets show for a given fire to close #58.
* adjusts text for when no tweets display.
* adds django template tag/filter to keep tweet text as safe but url-ify any links that begin with http or https to close #95
* adds display of inciweb narrative underneath current situation on details page.
* streamlines current situation between calfire and inciweb for display on details template. adds data source to if not created function to fill in the blanks.