removing web app capability from non-webapp pages

skip ActionCable for follow/unfollow/block events, instead clear UI from
blocked account's posts instantly if block request succeeds. Add forgotten
i18n for sensitive content

This prevents the undefined profile from being opened in the first place on such an error

It can take as much as 0.5s if not longer to complete

respect hub.lease_seconds (fix #46)

timeline reload in UI, other small fixes

behaviour with Turbolinks enabled, optimizing Rabl for production

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.