Modify roles and admin access

* Add submitter role
* Reserver access to /admin for Redactors+ only
Fix dashboard spec
Add submitter and normal user to db/seeds

Also add users for Adam, Wendy, and the thoughtbot team.
First failing integration spec

Refactor CurbHelper to (eventually) support adjusting headers
per-invocation.
Extract Class: SubmitNotice

DRYs up the controller now that we'll need to inject authentication code
in only the JSON format response. Makes testing a tad easier.
Implement token authentication