Merge pull request #8839 from mattdbridges/clarify_chdir

Clarify Dir.chdir definition
adding small mention one single line blocks in contributing to rails
[ci skip]
Merge pull request #8849 from mattdbridges/contributing_to_rails

Adding mention about single-line blocks in Contributing to Rails [ci skip]
Merge pull request #8848 from Irio/master

Set default value to ActiveModel::Validator initializer attribute
s/messqage/message/ in message_encryptor_test.rb
Merge pull request #8859 from tehgeekmeister/master

Fix a typo in a test.
adding start / finish on the instrumenter, adding tests for the class
extract logger and development checks to methods
adding missing requires
fire a notification when the request stops / starts
Remove redundant double quotation marks
update assets guide code styling

* 1.9 hash syntax
* proper formatting around one line blocks
* do-end for multiline blocks
add asset pipeline guides section on implementing & registering own engines
Clarified the minute option on DateTime#change
Merge pull request #8863 from zires/dev

Remove redundant double quotation marks [ci skip]
Merge pull request #8821 from jamis/master

Evaluate view_cache_dependencies at the instance level

Conflicts:
	actionpack/lib/action_controller/caching.rb
extract PerformanceTest into rails-performance_tests gem
remove performance tests from the default stack
remove the rails guide on performance testing
Merge pull request #8876 from senny/extract_performance_tests

Extract ActionDispatch::PerformanceTest