Fix #233, fix #268

Remove unneeded indices, improve error handling in background workers, don't needlessly reload reblogged status, send Devise e-mails asynchronously

to the API

registration API

respect hub.lease_seconds (fix #46)

The frontend will now be an OAuth app, auto-authorized. The frontend will use an access token for API requests
Adding better errors for the API controllers, posting a simple status works from the frontend now

in the pool, adding a throttle of 60rpm per IP, adding mini profiler, adding
admin status to users

POST /api/statuses                  Params: status (text contents), in_reply_to_id (optional)
GET  /api/statuses/:id
POST /api/statuses/:id/reblog

GET  /api/accounts/:id
GET  /api/accounts/:id/following
GET  /api/accounts/:id/followers
POST /api/accounts/:id/follow
POST /api/accounts/:id/unfollow

POST /api/follows                  Params: uri (e.g. user@domain)

OAuth authentication is currently disabled, but the API can be used with HTTP Auth.