dalli 2.7.6 fixed deprecation warning caused by using
`Rack::Session::Abstract::ID`.
This commit suppress warnings on ActionPack tests.

See:
https://github.com/petergoldstein/dalli/commit/9874a7c3ad67eb1e31cafba0a51966db4f0c7e42

Ref - https://github.com/turbolinks/turbolinks-rails/pull/3

railties uses method_source, activesupport does not.  I assume code was refactored and the dependency wasn't removed.

All modern Rubies ship JSON as part of stdlib.  Using the gem actually hurts multi-platform support due to build difficulties on Windows.

- Leftover from https://github.com/rails/rails/commit/93abf58787396661230f31c7a2f58c18f30dbec9.

This new adapter does get a little more intimate with the redis-rb gem's
implementation than I would like, but it's the least bad of the
approaches I've come up with.

This PR includes two changes for 2.0.0:

- Breaking API change around `async.perform` --> `perform_async`
- New addition of `perform_in`, which now allows end users of the
  adapter to use the `enqueued_at` public API method.

(as adapted to use concurrent-ruby / nio4r instead of eventmachine)

- adapter -> pubsub (re)rename internally
- Change variable names to match method names
- Add EventMachine `~> 1.0` as a runtime dependency of ActionCable
- Refactor dependency loading for adapters

- Eventmachine version gets updated when `bundle` is run locally.

This reverts commit d0393fcc, reversing
changes made to 3b7ccadf.

This removes 8 runtime gem dependencies from Rails:

```
Using hitimes 1.2.3
Using timers 4.1.1
Using celluloid-essentials 0.20.5
Using celluloid-extras 0.20.5
Using celluloid-fsm 0.20.5
Using celluloid-pool 0.20.5
Using celluloid-supervision 0.20.5
Using celluloid 0.17.2
```

- Followup of https://github.com/rails/rails/commit/bc194937ad6c1fa12bca73cfc05de39a97ba783d.

🎉 🍻

It will make sure that the generated application in the tests get the
gem.

Many CVEs released: https://groups.google.com/forum/#!topic/ruby-security-ann/aSbgDiwb24s

I didn't mean to commit that!