* Depend on websocket-driver >= 0.6.1

pg-1.0.0 is just released and most Gemfiles don't restrict
it's version. But the version is checked when connecting to
the database, which leads to the following error:

Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0

See also this pg issue:
https://bitbucket.org/ged/ruby-pg/issues/270/pg-100-x64-mingw32-rails-server-not-start

Preparation for pg-1.0 was done in commit f28a3310,
but the pg version constraint was not yet relaxed.

I often face the following error when running test/connection/client_socket_test.rb:

```
$ bin/test test/connection/client_socket_test.rb:38
Run options: --seed 44035

# Running:

F

Failure:
ActionCable::Connection::ClientSocketTest#test_delegate_socket_errors_to_on_error_handler
[/app/actioncable/test/connection/client_socket_test.rb:47]:
--- expected
+++ actual
@@ -1 +1 @@
-["foo"]
+["Broken pipe", "Broken pipe", "Broken pipe", "foo"]
```

It can be reproduced easily by applying the following patch:

```
diff --git a/actioncable/test/connection/client_socket_test.rb b/actioncable/test/connection/client_socket_test.rb
index 2051216010..6bb9f13ea7 100644
--- a/actioncable/test/connection/client_socket_test.rb
+++ b/actioncable/test/connection/client_socket_test.rb
@@ -34,7 +34,8 @@ def on_error(message)
     @server.config.allowed_request_origins = %w( http://rubyonrails.com )
   end

-  test "delegate socket errors to on_error handler" do
+  1000.times do |i|
+  test "delegate socket errors to on_error handler #{i}" do
     run_in_eventmachine do
       connection = open_connection

@@ -47,6 +48,7 @@ def on_error(message)
       assert_equal %w[ foo ], connection.errors
     end
   end
+  end

   test "closes hijacked i/o socket at shutdown" do
     run_in_eventmachine do
```

The cause is writing io from different thread at the same time.

`connection.process` sends handshake message from [StreamEventLoop's thread][] whereas
`connection.handle_open` sends welcome message from current thread.

[StreamEventLoop's thread]: https://github.com/rails/rails/blob/067fc779c4560fff4812614a2f78f9248f3e55f8/actioncable/lib/action_cable/connection/stream_event_loop.rb#L75

Make clear that the files are not to be run for interpreters.

Fixes #23847.
Fixes #30690.
Closes #23878.

Simplify our dev testing and CI story since we're also testing against
Redis for the Active Support cache store.

Directly test whether db, host, password, etc are passed through as
config instead of spinning up a Redis server with a password set on it.

Follow up of #31004.

- Backport commit: https://github.com/rails/rails/commit/7122a2cdc3634e170129f8b6cabd1e8fbed13c3d

This basically reverts f851e1f7

* Use `gem 'redis', '~> 4.0'` for new app Gemfiles
* Loosen Action Cable redis-rb dep to `>= 3.3, < 5`
* Bump redis-namespace for looser Redis version dep
* Avoid using the underlying `redis.client` directly
* Use `Redis.new` instead of `Redis.connect`

* When the adapter is missing, raise an exception that points out config
  typos and missing Gemfile entries. (We can assume that a non-builtin
  adapter was used since these are always available.)
* When loading an adapter raises a LoadError, prefix its error message
  to indicate that the adapter is likely missing an optional dependency.

If a frontend for some reason tries to unsubscribe from a non existing subscription, the following error is logged:

Could not execute command from ({"command"=>"unsubscribe", "identifier"=>"{\"channel\":\"SomeChannel\"}"}) [NoMethodError - undefined method `unsubscribe_from_channel' for nil:NilClass]

Instead, it will now properly log:

Could not execute command from ({"command"=>"unsubscribe", "identifier"=>"{\"channel\":\"SomeChannel\"}"}) [RuntimeError - Unable to find subscription with identifier: {"channel":"SomeChannel"}]

Don't use remove_method or remove_possible_method just before a new
definition: at best the purpose is unclear, and at worst it creates a
race condition.

Instead, prefer redefine_method when practical, and
silence_redefinition_of_method otherwise.

[ci skip]

And enable `context_dependent` of Style/BracesAroundHashParameters cop.

In some examples and guides we are recommending to use code like:

```ruby
verified_user = User.find_by(id: cookies.signed[:user_id])
```

My suggestion is to use instead:

```ruby
verified_user = User.find_by(id: cookies.encrypted[:user_id])
```

which invites users to prefer the "newer" encrypted cookies over the
"legacy" signed cookies.

Postgres --> PostgreSQL
ActionCable --> Action Cable

[ci skip]

(cherry picked from commit e2093c1f678175bde7c37c848686d979427346e1)
(cherry picked from commit d7dbe48273bd9e0adb1de5b52e3cdaeb4a65630b)

It is covered by following assertion.

This reverts commit 3420a145, reversing
changes made to afb66a5a.

- Adds RedisAdapterTest::AlternateConfiguration to account
  for a relatively common alternative setup, as it’s used
  as the first example in the
  [Redis rubygem](https://github.com/redis/redis-rb#getting-started)

- Supplies original RedisAdapterTest with more complete
  redis:// url format by adding a ‘userinfo’ (blank user),
  so that it resembles the alternate configuration

- Supplies original EventedRedisAdapterTest with more complete
  redis:// url as well

- Adds before_script to start redis-server with password as a daemon
  and with explicit defaults copied from the default redis.conf
  (Instead of using Travis' default init/upstart scripts for `redis` service)

Users should never publicly be interacting with an instance of this.  The instance that comes along with an `AC::Connection::Base` instance (the only thing a user should be working with) is [itself intended to be private](https://github.com/tjschuck/rails/blob/master/actioncable/lib/action_cable/connection/base.rb#L137-L140).

[ci skip]