as this can lead to confusing time stubbing.

     Instead of:

         travel_to 2.days.from_now do
           # 2 days from today
           travel_to 3.days.from_now do
             # 5 days from today
           end
         end

     preferred way to achieve above is:

         travel_to 2.days.from_now
         # 2 days from today

         travel_back
         travel_to 5.days.from_now
         # 5 days from today

Closes #24690
Fixes #24689

We are currently using `%e` which adds a space before the result if the
digit is a single number. This leads to strings like `February  2, 2016`
which is undesireable. I've opted to replace with 0 padding instead of
removing the padding entirely, to preserve compatibility for those
relying on the fact that the width is constant, and to be consistent
with time formatting.

Fixes #25251.

Follows the same pattern as controllers and jobs. Exceptions raised in
delivery jobs (enqueued by `#deliver_later`) are also delegated to the
mailer's rescue_from handlers, so you can handle the DeserializationError
raised by delivery jobs:

```ruby
class MyMailer < ApplicationMailer
  rescue_from ActiveJob::DeserializationError do
    …
  end
```

ActiveSupport::Rescuable polish:
* Add the `rescue_with_handler` class method so exceptions may be
  handled at the class level without requiring an instance.
* Rationalize `exception.cause` handling. If no handler matches the
  exception, fall back to the handler that matches its cause.
* Handle exceptions raised elsewhere. Pass `object: …` to execute
  the `rescue_from` handler (e.g. a method call or a block to
  instance_exec) against a different object. Defaults to `self`.

Use the updated changelog from the first merge: 7254517f

References #22806, #24762.

[ci skip]

This is just to remove astonishment from getting `3600 seconds` from typing `1.hour`.

Regression: adding minutes/hours to a time would change its time zone

This reverts commit 1bf9fe75.

This can be an issue when TZInfo::TimeZone#current_period is refreshed
due to timezone period transition, but it's not reflected in
ActiveSupport::TimeZone object.

For example, on Sun, 26 Oct 2014 22:00 UTC, Moscow changed its TZ from
MSK +04:00 to MSK +03:00 (-1 hour). If ActiveSupport::TimeZone['Moscow']
happens to be initialized just before the timezone transition, it will
cache its stale utc_offset even after the timezone transition.

This commit removes cache and fixes this issue.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

[ci skip]

Previously these methods could return either a DateTime or a Time
depending on how the ActiveSupport::TimeWithZone instance had
been constructed. Changing to always return an instance of Time
eliminates a possible stack level too deep error in to_time where
it was wrapping a DateTime instance.

As a consequence of this the internal time value is now always an
instance of Time in the UTC timezone, whether that's as the UTC
time directly or a representation of the local time in the timezone.

There should be no consequences of this internal change and if
there are it's a bug due to leaky abstractions.

Mirrors the Time#subsec method by returning the fraction
of the second as a Rational.

Mirrors the DateTime#sec_fraction method by returning the fraction
of the second as a Rational.

In Ruby 2.4 the `to_time` method for both `DateTime` and `Time` will
preserve the timezone of the receiver when converting to an instance
of `Time`. Since Rails 5.0 will support Ruby 2.2, 2.3 and later we
need to introduce a compatibility layer so that apps that upgrade do
not break. New apps will have a config initializer file that defaults
to match the new Ruby 2.4 behavior going forward.

For information about the changes to Ruby see:
https://bugs.ruby-lang.org/issues/12189
https://bugs.ruby-lang.org/issues/12271

Fixes #24617.

That helper will return time zones for any country that tzdata knows about.
So it will be much simpler for non-US people to list own country time zones
in HTML selects or anywhere.

Ruby 2.4 introduces `Array#sum`, but it only supports numeric elements,
breaking our `Enumerable#sum` which supports arbitrary `Object#+`.
To fix, override `Array#sum` with our compatible implementation.

Native Ruby 2.4:

    %w[ a b ].sum
    # => TypeError: String can't be coerced into Fixnum

With `Enumerable#sum` shim:

    %w[ a b ].sum
    # => 'ab'

We tried shimming the fast path and falling back to the compatible path
if it fails, but that ends up slower even in simple causes due to the cost
of exception handling. Our only choice is to override the native `Array#sum`
with our `Enumerable#sum`.

```ruby
ActiveSupport::Duration.parse('P3Y6M4DT12H30M5S')

(3.years + 3.days).iso8601
```

Inspired by Arnau Siches' [ISO8601 gem](https://github.com/arnau/ISO8601/)
and rewritten by Andrey Novikov with suggestions from Andrew White. Test
data from the ISO8601 gem redistributed under MIT license.

(Will be used to support the PostgreSQL interval data type.)

- Raised an argument error if no block is passed to #fetch with
'force: true' option is set.
- Added tests for the same.

This is just to remove astonishment from getting `3600 seconds` from typing `1.hour`.

Previously `String#to_time` returned the midnight of the current date
in some cases where there was no relavant information in the string.
Now the method returns `nil` instead in those cases.

Fixes #22958.

The native DateTime#<=> implementation can be used to compare instances
with numeric values being considered as astronomical julian day numbers
so we should call that instead of returning nil.

Fixes #24228.

By default, this method formats US number. This commit extends its
functionality to format number for other countries with a custom regular
expression.

    number_to_phone(18812345678, pattern: /(\d{3})(\d{4})(\d{4})/)
    # => 188-1234-5678

The output phone number is divided into three groups, so the regexp
should also match three groups of numbers.

[ci skip]

Sync AV, AR, AJ, AS, AM changelogs with our 5.0 release notes draft.
This is a follow up to c94045dc and contains changes made since the
release of beta1.

Fix a bug in `Marshal.load` that caused it to loop indefinitely when
trying to autoload a constant that resolved to a different name.

This could occur when marshalling an ActiveRecord 4.0 object (e.g. into
memcached) and then trying to unmarshal it with Rails 4.2. The
marshalled payload contains a reference to
`ActiveRecord::ConnectionAdapters::Mysql2Adapter::Column`, which in
Rails 4.2 resolves to
`ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter::Column`.

These should allow external code to run blocks of user code to do
"work", at a similar unit size to a web request, without needing to get
intimate with ActionDipatch.

After Ruby 1.9, we can easily get the constants that have been
defined locally by `Module.constants(false)`.

When building decorators, a common pattern may emerge:

    class Partition
      def initialize(first_event)
        @events = [ first_event ]
      end

      def people
        if @events.first.detail.people.any?
          @events.collect { |e| Array(e.detail.people) }.flatten.uniq
        else
          @events.collect(&:creator).uniq
        end
      end

      private
        def respond_to_missing?(name, include_private = false)
          @events.respond_to?(name, include_private)
        end

        def method_missing(method, *args, &block)
          @events.send(method, *args, &block)
        end
    end

With `Module#delegate_missing_to`, the above is condensed to:

    class Partition
      delegate_missing_to :@events

      def initialize(first_event)
        @events = [ first_event ]
      end

      def people
        if @events.first.detail.people.any?
          @events.collect { |e| Array(e.detail.people) }.flatten.uniq
        else
          @events.collect(&:creator).uniq
        end
      end
    end

David suggested it in #23824.

Adds changelog headers for beta3 release