* 'master' of github.com:yiisoft/yii2: (23 commits)
  datepicker should show empty field when value is empty string
  complete docs about Nav to include the style
  Update tutorial-mailing.md
  Reverted #3665 (reverted from commit 2aa39499)
  Unit test for `yii\console\controllers\AssetController` advanced
  Doc comments for `yii\console\controllers\AssetController` extended
  `yii\console\controllers\AssetController` now handles bundle files from external resources properly
  skip requirements checker test on HHVM
  Update README.md in guide-es [skip ci]
  Add helper-array.md in guide-es [skip ci]
  a note about database naming style
  Add syntax highlighting [skip ci]
  docs/guide-ja/tutorial-core-validators.md - completed [ci skip]
  docs/guide-ja/tutorial-core-validators.md - WIP [ci skip]
  docs/guide-ja/tutorial-core-validators.md - WIP [ci skip]
  Fixed `\yii\authclient\OAuth2::refreshAccessToken()` does not save fetched token
  `\yii\authclient\AuthAction::defaultCancelUrl()` changed to use `yii\web\User::loginUrl`
  MongoDB PHP extension min version raised up to 1.5.0
  Были различные ссылки в русском гайде - привел все к английскому виду ссылки. Файлы по этим ссылкам еще не существуют поэтому переименовывать их и не нужно.
  Fixed typo.
  ...