Move async execution from celluloid to concurrent-ruby

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
```

2 files changed, 0 insertions, 7 deletions

diff --git a/actioncable/test/test_helper.rb b/actioncable/test/test_helper.rb
index 12dcd98402..325305939f 100644
--- a/actioncable/test/test_helper.rb
+++ b/actioncable/test/test_helper.rb
@@ -14,11 +14,6 @@ require 'rack/mock'
 # Require all the stubs and models
 Dir[File.dirname(__FILE__) + '/stubs/*.rb'].each {|file| require file }
 
-$CELLULOID_DEBUG = false
-$CELLULOID_TEST  = false
-require 'celluloid'
-Celluloid.logger = Logger.new(StringIO.new)
-
 require 'faye/websocket'
 class << Faye::WebSocket
   remove_method :ensure_reactor_running
diff --git a/actioncable/test/worker_test.rb b/actioncable/test/worker_test.rb
index 69c4b6529d..9911a3b98b 100644
--- a/actioncable/test/worker_test.rb
+++ b/actioncable/test/worker_test.rb
@@ -17,8 +17,6 @@ class WorkerTest < ActiveSupport::TestCase
   end
 
   setup do
-    Celluloid.boot
-
     @worker = ActionCable::Server::Worker.new
     @receiver = Receiver.new
   end