* Update RAILS_VERSION
* bundle (with Ruby 2.6)
* rake changelog:header

* Update RAILS_VERSION
* Bundle
* rake version
* rake changelog:header

The queue_classic gem before version 3.1.0 was locked to patch releases
of the pg gem so bump the version up from 0.3.2 - unsure how this ever
worked with 0.3.2 as QC::Setup module didn't exist until version 2.0.0.

Even with using queue_classic-3.1.0 it still has an upper bound of < 0.19.0
so we need to reduce our pg upper bound so that bundler will resolve.

Rails 4.2 will never be compatible with pg-1.0 or later so no need
to be warned about constants being removed and also prevent weird
bundler resolution with early queue_classic and pg-1.1.3.

Sidekiq 5.1.3 fixes the version check on Ruby 2.2.10.

See flavorjones/loofah#144

Newer versions of resque-scheduler use the new hash syntax which means
they won't work with Ruby 1.9.3.

This commit locks resque-scheduler to an older version when we're using
less than Ruby 2.0.0

Fixes:

```
def evalsha(script, keys, argv, refresh: false)
                                        ^
/home/travis/build/rails/rails/vendor/bundle/ruby/1.9.1/gems/resque-scheduler-4.3.1/lib/resque/scheduler/lock/resilient.rb:78: syntax error, unexpected keyword_end, expecting $end
```

Somehow travis installed queue classic 0.3.2. 0.3.2 causes the following
error:

```
1) Error:
AdapterTest#test_perform_job_logging:
URI::InvalidURIError: bad URI(is not URI?):
```

This change sets the lock file to install above 0.3.2. I'm not sure what
folks are using in production but this prevents the oldest version like
that from being installed on travis.

Uglifier 4.0.1 doesn't work without Sprockets 3.7.1. Since 4.2 isn't
really getting updates we should try to at least maintain a green build.

Fixes the following errors:

Build ref: https://travis-ci.org/rails/rails/jobs/313152105#L777
Build ref: https://travis-ci.org/rails/rails/jobs/313152105#L772

An update to mail broke some tests on Rails. Originally they were
unblocked here #31026 but Jeremy fixed them for Mail 2.7 in
0931e17e.

I wasn't able to cleanly backport this so I'm doing it manually. Fixes
the failing Rails 4.2 build on travis.

The new version has some minor issues, and old release branches
traditionally keep their theme anyway.

Version 0.3.6 includes fixes for the Fixnum warnings on Ruby 2.4.

Version 1.3.13 includes the proper fix for the segfaults reported
in sparklemotion/sqlite3-ruby#195.

This is a bit over-constraining for the committed lock file, but Travis
ignores that anyway.

As demonstrated in #25880 the to_time method converts the utc time
instance to a local time instance which is an expensive operation
so since ActiveSupport::TimeWithZone is a value object and shouldn't
be mutated we can safely cache it without worrying about invalidation.

For some reason bundler is trying to install serverengine 2.0.0 which
requires Ruby 2.1.0 or greater so use any version of sneakers less than
2.0.0 which introduces it's own minimum requirement for Ruby 2.0 which
we can't use as Rails 4.2 supports Ruby 1.9.3.