provide a builder for form labels to customize wrapping around I18n content
add I18n support for `:placeholder` HTML option is passed to form fields
just use the placeholder tag value if it is passed as a String
Follow-up to #16560

For the sake of backward-compatibility, we need to make #instance_of?
return true for Fixnum. On the other hand, the method should still
give true for ActiveSupport::Duration itself which was not the case
before.
Skip #eql? tests on Rubinius for AS::Duration

Since Rubinius is relying on #instance_of? for its definition of #eql?
(http://git.io/MtmbbA) but ActiveSupport::Duration should behave like
is_a? it returns true with `Fixnum`.

Thus, for the moment, the last assertion is failing so we have to skip
this test.
treetop is no longer a mail (rails) dependency

see https://github.com/mikel/mail/commit/2da7c7985c221272f6451b27ab8b41e84e0a6804
Address comments on Gzip implementation

- don't mutate PATH_INFO in env, test
- test fallback content type matches Rack::File
- change assertion style
- make HTTP_ACCEPT_ENCODING comparison case insensitive
- return gzip path from method instead of true/false so we don't have to assume later
- don't allocate un-needed hash.

Original comments:

https://github.com/rails/rails/commit/
cfaaacd9763642e91761de54c90669a88d772e5a#commitcomment-7468728

cc @jeremy
Merge pull request #16680 from huoxito/update-dependencies

treetop is no longer a mail (rails) dependency [ci skip]
Merge pull request #16616 from schneems/schneems/jeremy-comments

Address comments on Gzip implementation
Merge pull request #16662 from robin850/duration-instance-of

Fix `ActiveSupport::Duration#instance_of?` to behave like `#is_a?`
[ActiveJob] Add activesupport as dependency [ci skip]
Merge pull request #16639 from agrobbin/input-placeholder-i18n

Add I18n support for `:placeholder` HTML option is passed to form fields
Merge pull request #16681 from seuros/master

[ActiveJob] Add activesupport as dependency [ci skip]
pg, `default_sequence_name` needs to return a string.

This is a reacon to https://github.com/rails/rails/commit/d6c1205584b1ba597db4071b168681678b1e9875#commitcomment-7502487
This backwards incompatibility was introduced with d6c12055 to fix #7516.
However both `connection.default_sequence_name` and `model.sequence_name` are public API.
The PostgreSQL adapter should honor the interface and return strings.

/cc @matthewd @chancancode
Merge pull request #16488 from agrobbin/form-label-builder

Provide a builder for form labels to customize wrapping around I18n content
[ci skip] use proper apostrophe
Merge pull request #16690 from ankit1910/proper-use-of-aporstrophe

[ci skip] use proper apostrophe