Active subscribers

[ChaituVR]

Fixes #21

Tasks for @bonustrack

• Make sure to run these:

ALTER TABLE subscribers
ADD COLUMN last_attempt int DEFAULT 0 NOT NULL AFTER space;

ALTER TABLE subscribers
ADD COLUMN last_active int DEFAULT 0 NOT NULL AFTER space;

ALTER TABLE
  `subscribers` MODIFY `created` TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL;

ALTER TABLE
  `subscribers` MODIFY `active` int DEFAULT 1 NOT NULL;

Update subscribers set created = now();
Update subscribers set active = 1;