Renamed HeaderCollection::addDefault to setDefault.
Fixes issue #234: Added Html::addCssClass() and removeCssClass().
code style fixes
added namespace to locale command
typo fix.
Fixed a bug in ExpressionDependency.
refactored cache dependency methods.
Added GroupDependency.
Fixes issue #421: yii\db\Schema:refresh() does not clear all cache
Removed ProfileTarget.
Refactored the way of sending response in controller actions.
Errorhandler, manually load classes

load ErrorException manually because autoloading them will not work
when error occurs while autoloading a class
Fixes for issue #536: refactored error handler.
Refactored console controller color option.
fixed how console color should be enabled.
Replaced Jsonable with Arrayable.
Added support for different response formats.
Support for error response in different formats.
fix MigrateController
Merge pull request #537 from sergon/patch-4

fix MigrateController
Moved toArray() from YiiBase to ArrayHelper.
Merge branch 'master' of github.com:yiisoft/yii2