update directory tree in the generated README

[ci skip]

Fix missing spaces in method definitions

Adding a usage message to install.rb script

Previously, invoking the install.rb script with zero arguments
caused it to attempt to install all gems without a version
suffix, which would fail spectacularly. Failing gracefully with
a usage message is more helpful to a first-time user.

A small fix for an AR test case

Remove a useless TODO comment

Rename update_attributes method to update

Typo and grammar fixes in the ActionPack CHANGELOG

Fix env toggling, improve error page styling

Fix typo on form_tag_helper.rb [ci skip]

The inline documentantion had a typo that was somewhat confusing.

test PATCH method for update action in generated scaffold controller test rather than PUT

Refactor Routing::Mapper#matches?

Pass in `--local` when doing `gem install` for local gems. [ci skip]

Explain the possible IP precautions

Restore original remote_ip algorithm.

Proxy servers add X-Forwarded-For headers, resulting in a list of IPs. We
remove trusted IP values, and then take the last given value, assuming that
it is the most likely to be the correct, unfaked value. See [1] for a very
thorough discussion of why that is the best option we have at the moment.

[1]: http://blog.gingerlime.com/2012/rails-ip-spoofing-vulnerabilities-and-protection/

Fixes #7979

Remove another unnecessary dup

Conflicts:
	activerecord/lib/active_record/dynamic_matchers.rb

do not append a second slash when using `trailing_slash: true`

Fix a number of validation/style errors