- Escape the channel name when subscribing in PG
- Refactor popping the queue to make it easier to read

We now only create one adapter instance for the server, so it can hold
the listener. This in turn allows the listener to get the PG connection
from the adapter, which will be a good place to allow more flexible
configuration.

Association Guide replaces Order as example with Author-Book Example …

fixes #21500

Add clarification about `first` and `last` behavior when using `order` [ci skip]

Checked in changes to Gemfile.lock on latest master

Updated the guides for having a distinct has_many through at the data…

[ci skip] Improve Action Cable configuration explanations

The current example

    add_index :person_articles, :article, unique: true

Does not work, the `:article` column does not exist as it will be
a join table (based on the prior example) so should use :article_id

The documentation seems to suggest that it will allow an article to
be added only once to a person via the join table, what actually
occurs is that it only allows the article to be added to one person,
at which point it should be a `belongs_to` association.

Also changed the new example to use readings based on the prior example

Explain how HStore columns can be queried [ci skip]

- Fixes #22876.

Pass through AP CHANGELOG

* Clarify wording around how defaults work
* Clarify wording around what formatting versus information is required
* Separate consumer configuration section since it is important and wordy
* Add additional explanation of options for setting consumer configuration
* Consolidate consumer configuration information to reduce confusion

Remove AV dependence on AP's Mime

Enrich Action View Template types with symbols from Action Dispatch Mime.

A Set can't be implicitly converted into an Array:

```
irb(main):012:0> formats = [ :rss ]
=> [:rss]
irb(main):013:0> formats &= SET.symbols
TypeError: no implicit conversion of Set into Array
    from (irb):13:in `&'
    from (irb):13
    from /Users/kasperhansen/.rbenv/versions/2.2.3/bin/irb:11:in `<main>'
```

Besides `Mime::SET.symbols` returns an Array, so we're closer to that.

Match `Mime::SET.symbols`.

If they aren't symbols, then they aren't likely to be in the set anyway.

We'll be using this to map over to Action Dispatch's Mime::Set.

The template types is a private abstraction to fill in basic blanks from Action Dispatch's
mime types. As such we can modify the data structure ourselves.

Spares a to_sym call by aliasing to_sym to ref.

Then the delegate felt meager for one method; ditch and define method ourselves.

The @symbol has already been converted to a symbol in initialize, so no need to call to_sym
when comparing it.

Ditch early return for a simple unless statement.

We delegate to_sym to the internal symbol, which we've already called to_sym on in
initialize, so we don't need to do that.

We also know to_sym will never return a falsy value, so we'll never hit to_s.

Just return the symbolized symbol.

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

In commit d993cb36 `build_path` was changed from using `grep` to
`find_all` to save array allocations.

This change was a little too aggressive in that when the dash comes
before the symbol like `/omg-:song` the symbol is skipped.

Removing the check for `n.right.left.literal?` fixes this issue, but
does add back some allocations. The number of allocations are still well
less than before.

I've added a regression test to test this behavior for the future.

Fixes #23069.

Array allocations as of d993cb36:

```
{:T_SYMBOL=>11}
{:T_REGEXP=>17}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_OBJECT=>91009}
{:T_DATA=>100088}
{:T_HASH=>114013}
{:T_STRING=>159637}
{:T_ARRAY=>321056}
{:T_IMEMO=>351133}
```

Array allocations after this change:

```
{:T_SYMBOL=>11}
{:T_REGEXP=>1017}
{:T_STRUCT=>6500}
{:T_MATCH=>12004}
{:T_DATA=>84092}
{:T_OBJECT=>87009}
{:T_HASH=>110015}
{:T_STRING=>166152}
{:T_ARRAY=>322056}
{:T_NODE=>343558}
```

Avoid multiple default paths to server.pid file

Fix bug (#22811) that occurs when rails server is started in daemon mode
and optional path to the `server.pid` file is omitted. Store default path
in a constant instead of evaluating it multiple time using `File.expand_path`.

The bug in detail: The server startup procedure crashes, since it tries to
open a file at `/tmp/pids/server.pid` instead of
`<path to project>/tmp/pids/server.pid`. This bug was introduced in 51211a94
when Rack was upgraded from version 1.x to 2.x. Since version 2.x,
Rack does not memoize the options hash [1], and as a consequence
`Rails::Server#default_options` will be evaluated multiple times.
The hash returned by `Rails::Server#default_options` holds the default path
to the `server.pid` file. The path is generated with the method
`File.expand_path`. However, the return value of this method depends on the
current working directory [2], which changes once `Process.daemon` is invoked
by `Rack::Server#daemonize_app` and the process is detached from the current
shell.

Close #22811

[1]https://git.io/vzen2
[2]http://ruby-doc.org/core-2.1.5/File.html#method-c-expand_path