CYB-51 https://jira.ets.berkeley.edu/jira/browse/CYB-51

Provide submissions data to the Gallery front-end

* collects the data when the submissions are processed by the Sidetiq (cron) job
* provides the data so collected to an api call (/api/v1/gallery/index(.json)).
Merge pull request #43 from coyote/api_gallery_controller

CYB-51 https://jira.ets.berkeley.edu/jira/browse/CYB-51