DLTP-227 File Thumbnail changes.

* The thumbnail/representative image on a work should be clickable and
  when clicked direct the user to the downloaded file for that
  representative file.
* On index page thumbnail should link to show page for curate concern.

dltp-227#

Fix file selection for link on thumbnail to representative image instead of just the first one.

Remove unnecessary line that was causing an error.

Fix one rspec test, add additonal rspec test for Article.

Correct extra tab spacing.
Adding curation_concern paths

Woe is me. In creating the curation_concern namespace, the polymorphic
routes continue to be a scourge. This is evident when we are rendering
objects from SOLR that are not part of the curation_concern namespace.

For example: People and Collections
Merge pull request #51 from ndlib/dltp-227

DLTP-227 File Thumbnail changes.