Merge branch '1.6'

Conflicts:
	package/codecept.phar
	src/Codeception/Codecept.php
waitForElementChange() callback return value was not being used
Merge pull request #667 from wheelsandcogs/wait-for-element-change-fix

waitForElementChange() callback return value was not being used
version bump
Merge branch '1.7' of github.com:Codeception/Codeception into 1.7
version bump
release branch changed to 1.8
docs updated
phpunit test bootstrap file fix
Placeholder\Registry::unsetRegistry() should only be used with < 2.2.0 

Currently the ZF2 module will trigger errors, causing failures with ZF >= 2.2.0, as the placeholder view helpers no longer use singleton registries.
Added a compareVersion call to check for < 2.2.0 to still conditionally reset the singleton registry for only appropriate versions of ZF2.
Merge pull request #669 from Bittarman/patch-1

Placeholder\Registry::unsetRegistry() should only be used with < 2.2.0
Merge branch 'master' of https://github.com/Codeception/Codeception

Conflicts:
	package/codecept.phar
	src/Codeception/Codecept.php
	src/Codeception/Command/Base.php
Merge branch '1.7' of https://github.com/Codeception/Codeception

Conflicts:
	package/codecept.phar
	src/Codeception/Codecept.php
	src/Codeception/Module.php
	src/Codeception/PHPUnit/Constraint/CrawlerNot.php
	src/Codeception/Util/Mink.php
Merge branch '1.8' of https://github.com/Codeception/Codeception

Conflicts:
	package/codecept.phar
	src/Codeception/Codecept.php
	src/Codeception/Module.php
code cleanup and code style (PSR-2) fixes in commands
fix test
Fixed Yii2 statusCode

We changed the default value to 200 and removed the possibility to set it to null.
Merge pull request #691 from cebe/patch-1

Fixed Yii2 statusCode
Merge pull request #693 from tiger-seo/master

(2) fixing November 9th merge issues, code style fixes, small refactrorings
Missing brackets attempt 2

:)