Updating flickr app.

 * new data source (mongodb: localhost -> tangelo -> flickr_paris)
 * displaying image data via url property
Adding flickr data retrieval script.

This also includes changes to the flickr app to reflect a more "native" form of
data (closer to the fieldnames delivered by the Flickr API itself).
Added data prep documentation about Flickr app.
Adding data retrieval script, updating app to display message about data prep docs
Merge branch 'flickr-api-data'