Remove unnecessary ruby version comments

Update guide to reflect browser compatibility for HTTP verbs

Additional explanation about cache implementations

Bump Travis ruby version to 2.4.1

Fix duplicable? for Rational and Complex on ruby master, since they are now duplicable

Move comment to inside the method [ci skip]

Because this comment is not document for `supports_ranges?`

ref: https://github.com/rails/rails/pull/27636#discussion_r107560081

Remove `CollectionProxy#uniq`

Since #28473 `uniq` is delegated to `records`, so `CollectionProxy#uniq`
is unnecessary.

Document AC::Connection::Authorization#reject_unauthorized_connection

List options for `rails new --webpack=WEBPACK`

This method is repeatedly used throughout the docs (in the [AC::Connection docs](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/lib/action_cable/connection/base.rb#L28), the [AC README](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/README.md#a-full-stack-example), the [AC Guides](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/guides/source/action_cable_overview.md#connection-setup)), but not actually documented itself and seemingly not supported for public use based on its current `private` status.

This actually makes the method public and documents it.  The actual behavior that’s documented here is implemented [here](https://github.com/rails/rails/blob/12b684985837bc8ee9ad15c174cf4e07ca82d7c4/actioncable/lib/action_cable/connection/base.rb#L213-L219), via [this rescuing of the UnauthorizedError](https://github.com/rails/rails/blob/3dd1de8ba4d5862b01e7f5dd3878b21fd98b443b/actioncable/lib/action_cable/connection/base.rb#L172).

The method is [already tested here](https://github.com/rails/rails/blob/25473baf409185638073fe2f016f4b9dda284e50/actioncable/test/connection/authorization_test.rb#L17-L29).

[ci skip]

Change AD::ParamsParser::ParseError deprecation so it can be rescued

Correctly reset ARGV for "rails runner `CODE' arg arg arg..."

CLI arg "host" has precedence over ENV var "host"

Fix `LogSubscriber` to allow legacy `binds`

Don't add a dummy API key to every new Rails app

When you type `rails new -h`, the `--database=DATABASE` options display
this useful message:

> Preconfigure for selected database (options: mysql/postgresql/sqlite3/oracle/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)

However, the `--webpack=WEBPACK` option only displays this:

> Preconfigure for app-like JavaScript with Webpack

so it's hard to know *which* values are valid for `WEBPACK`.

This commit improves the help message to display:

> Preconfigure for app-like JavaScript with Webpack (options: react/vue/angular)

The implication of this commit is that the list needs to be manually updated
whenever rails/webpacker adds support for a new framework.

However, I don't imagine this list to change very frequently, and I think that
the benefit of display the list to the users is greater than the hustle of
updating the list when needed.

Fix `assert_logged` failure

[ci skip]

Don't comment out config.file_watcher during Rails upgrade

Suppress `WARNING:  nonstandard use of \\ in a string literal` warning

Tried to make the sentence read more clearly.

[ci skip]

Every new Rails app is currently generated with
`Rails.application.secrets[:api_key]` set to `123`.

This comes from a line in `config/secrets.yml` that, in my opinion,
should be left commented out to only serve as a syntax example, rather
than being actually set in every Rails app.

Additionally, we might want to give a better example than `123`, since
in the same file we are suggesting to

> Make sure the secret is at least 30 characters and all random,
> no regular words or you'll be exposed to dictionary attacks.

The result of this commit is that `config/secrets.yml` will include something like:

```yaml
 # Shared secrets are available across all environments.

 # shared:
 #   api_key: f56930851993982510d5bd9236f4108f6fe7c15448f1c6923a51872e0dbae1a24d274b318abb6518b540dfb51079c61640885f607467e5ed1053849be7587d61
```

rather than this:

```yaml
 # Shared secrets are available across all environments.

 shared:
   api_key: 123
```

These tests double-stub connection.pubsub, so we need to ensure the
first call's completed before we set up for the second.

https://www.ruby-lang.org/en/news/2017/03/22/ruby-2-4-1-released/

by setting `escape_string_warning = off`

Follow up of #27939.

`'#{name}' file doesn't exist, so no dependencies` was removed in
bb048147.

[PostgreSQL] Replace deprecated PG constants.

Stop complaining about not being able to digest dynamic template partial names and simplify error logging to a single line when not