realpath(false) = current working directory.
This can cause problems with getAlias() which returns false.

see yiisoft/yii#3113

fixes yiisoft/yii#2844

which resulted in endless loop

http://www.yiiframework.com/forum/index.php/topic/50982-cfilehelper-bug-security-flaw/

Added `yii\web\Request::get($name = null, $defaultValue = null)` and `yii\web\Request::post($name = null, $defaultValue = null)`

CS fix.

fixes #2093

issue #2093

- Gii diff markup is now copy paste friendly
- Removed StringHelper::diff()
- Moved phpspec/php-diff dependency from yiisoft/yii2 to yiisoft/yii2-gii

Fixes #2157: The '*' category pattern will match all categories that do not match any other patterns listed in `I18N::translations`

Allow writing widgets using return instead of echo in the run method to make it consistent with controller