Added background linting

Background hasChangedSignificantly is soon!
Merge pull request #885 from codecombat/master

Merge master into worker-lint
hasChangedSignificantly async refactor

Still checking for bugs
Removed some old code that didn't work out.
Archiving the script I used to migrate emailSubscriptions to emails.
Fixed race condition
Don't require CocoModel instantiation before schemas are included. Reload neutral spells on reload. Fix for adding Components to Thangs. Surface background: darkness, no parents.
Merge branch 'master' of https://github.com/codecombat/codecombat
Added background transpile
Removed superfluous comment
Renamed test_worker to aether_worker
Removed web worker logging listener
Merge pull request #894 from codecombat/feature/worker-lint

Background linting/transpilation/hasChangedSignificantly
Merge pull request #895 from codecombat/master

Merge master into production