tests improved, verify added
Some code style fixes [skip ci]
Ukrainian translations
Merge pull request #1941 from yiiframework-com-ua/uk_translate

Ukrainian translations
Merge pull request #1940 from lucianobaraglia/some-cs-fixes

Some code style fixes [skip ci]
Fixes #1921: Grid view ActionColumn now allow to name buttons like `{controller/action}`
Migration command show correct directory path while it not exist
Merge pull request #1942 from creocoder/migrate-command-fix

Migration command show correct directory path while it not exist
ModelSerializer WIP
Fixed typo in Russian messages
Fixed typo in Russian translation
Changed extensions's guide section about namespaces once again
fixed typo
MongoDB Session class added.
MongoDB Cache class added as draft.
Merge pull request #1944 from klimov-paul/mongodb-session

MongoDB Session class
Add French Translation
Merge branch 'master' of github.com:yiisoft/yii2 into mongodb-cache
Merge pull request #1948 from marsuboss/add_language_french

Add French Translation
Unit test for MongoDB Cache advanced.