Added embed/image.html.twig template
Merge pull request #117 from ezsystems/image_embed_template

Added embed/image.html.twig template
Implemented premium subscriber content

A custom location view provider displays a teasing template
if the content is Premium (section id 7 (Premium)), and if the
user doesn't have the subscriber role (id: 6)

Tests fail because the demo data isn't updated yet, but they
pass with the proper data.