improve wording of the engines guide

* "very minor" -> "subtle"
* reword successive sentences so that they don't begin with the same
  word ("this")
* "also" is not used in the end of the sentence, use "as well" instead
* "the reason is because" -> "the reason is that"
more woring improvements to the engines guide

* "also in ... is ..." -> "in .. there is ..."
* use "as well" instead of "also" in the end of the sentence
* "has the ability" -> "can"
refactor ShowExceptions' #call to use def-rescue instead of begin-rescue
Merge pull request #8798 from goshakkk/show-exceptions-begin-rescue

Refactor ShowExceptions' #call to use def-rescue instead of begin-rescue
access `@path` and `@routes` via reader methods in journey
Merge pull request #8799 from goshakkk/ivar-readers

Access ivars via instance reader methods for consistency
Instance_variable_names are strings. That is the most important information IMO
Don't require 'turn' from rails/test_help

If 'turn' is in the Gemfile with `:require => nil`, Rails should
respect that.

This supports the case where 'turn' may or may not be required
depending on different developers' preference or environment. E.g., you
require turn for local testing, but not on your CI server by putting
this in `test/test_helper.rb`:

    require 'turn' if ENV['TURN']
Update guides/source/getting_started.md

Reflect change in 009873a that renamed the script/ folder to bin/
improve StrongParameters documentation [ci skip]
Revert some warning removals related to Ruby 2.0

These warnings were actually a bug in Ruby 2.0, the accessors should not
be raising such warnings, they are only meant for ivars.

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Revert "fix warnings in Ruby 2.0"

This reverts commit 26702a6d3461f4a1c75165030b96886514ecb877.

-

Revert "Merge pull request #8282 from arunagw/warning_removed_for_ruby2"

This reverts commit f63d6544e45e78cda29c0c56fbdf3d9e1f405340, reversing
changes made to 3a890681fad8218305585036abed6d7463a44e41.
Merge pull request #8773 from goshakkk/guides-page-titles

Place article name in the beginning of guides page title
Merge pull request #8803 from frodsan/sp_docs

Improve StrongParameters documentation [ci skip]
Fix named scope + class method example

Closes #8804 [ci skip]
let the rails gem ship with the README

The doc:rails application rake task needs this README.
doc/README_FOR_APP is no longer generated
new README generated for new apps
Reset AR::Migration.verbose change to avoid depending on test run order
Reset test data, and fix bug that the inserted data were not actually selected
Fix readme tests

Related to the change introduced in 6cf47c533d7d6784d34fc31406a335555e0c32b8.