"Item" parameter keys are the values of the checkbox list,
while the values are the checkbox labels.

code style section has been added here:
https://github.com/yiisoft/yii2/wiki/Core-framework-code-style#self-vs-static

verification code for properties:
https://gist.github.com/cebe/7566916

defaults overided settings

It was mentioned in AssetManager::publish phpdoc.

added version, csrfVar and csrfToken to yii js module.

- Equals sign is now replaced with dot.
- Slash is now replaced with dash.
- Better phpdoc.

- rename FileHelper::mkdir for API consistency
- changed default permission for directories to 775 instead of 777
- added some properties to classes that deal with files to allow control
  over directory permissions.

`generateSalt` parameter validation fix.

fixes #33