Views for badge sharing-url #400

includes sharing url in actions tab for templates
shared url message in badge template view page
import button in directory for templates
styles and js for modal when sharing badge url's #400
Initial commit for sharing backend
Changes
Adding `slug` column to badge model
Share updates
 - using badge slug
 - getting single badge (not many!)
 - fixing some error handling
Creating badge slugs
Fixing `accepts` logic
Post-badge consumption
Fixing error handling
Sharing backend
Reducing character set to hex values only
First pass at sharing templates
Merge pull request #404 from mozilla/url-sharez

URL sharez