Make Code#value mass-assignable to fix issue with code import.
use url helper so links also work in production, see #34
Use consistent /unauthorized page.
Merge pull request #38 from rjackson/fix_unauthorized_access

Use consistent /unauthorized page. Closes #36.
Update successful pairing display. Closes #39.
Merge pull request #41 from rjackson/change_code_display

Update successful pairing display. Closes #39.