Method assertArraySubset in src/Codeception/Util/Shared/Asserts.php is public but should be protected

[damian-sikora-droptica]

After this change:
31e1f10

some additional test (Assert array subset) is added automatically to Cest class when Assert trait is used and it is throwing following error:

1) BlogCest: Assert array subset
 Test  tests/acceptance/BlogCest.php:assertArraySubset
                                                                                                                                        
  [PHPUnit_Framework_Exception] Argument #1 (No Value) of PHPUnit_Framework_Assert::assertArraySubset() must be a array or ArrayAccess  
                                                                                                                                        
/root/composer_codecept/vendor/phpunit/phpunit/src/Framework/Assert.php:63
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Util/Shared/Asserts.php:388
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Lib/Di.php:127
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Test/Cest.php:136
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Test/Cest.php:148
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Test/Cest.php:82
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Test/Test.php:87
/root/composer_codecept/vendor/phpunit/phpunit/src/Framework/TestSuite.php:722
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/PHPUnit/Runner.php:106
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/SuiteManager.php:157
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Codecept.php:188
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Codecept.php:157
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Command/Run.php:341
/root/composer_codecept/vendor/symfony/console/Command/Command.php:264
/root/composer_codecept/vendor/symfony/console/Application.php:869
/root/composer_codecept/vendor/symfony/console/Application.php:223
/root/composer_codecept/vendor/symfony/console/Application.php:130
/root/composer_codecept/vendor/codeception/codeception/src/Codeception/Application.php:103
/root/composer_codecept/vendor/codeception/codeception/codecept:36

Codeception v2.3.4
PHPUnit 5.7.21
PHP 5.6.30

it is the same with php 7.0 and PHPUnit 6

I think this method is treated as test because it is public
public function assertArraySubset

and should be protected like rest of methods in this trait