Update README.md

"creocoder/yii2-nested-set-behavior": "*":

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - The requested package creocoder/yii2-nested-set-behavior could not be foun
d in any version, there may be a typo in the package name.

Potential causes:
 - A typo in the package name
 - The package is not available in a stable-enough version according to your min
imum-stability setting
   see <https://groups.google.com/d/topic/composer-dev/_g3ASeIFlrc/discussion> f
or more details.

Read <http://getcomposer.org/doc/articles/troubleshooting.md> for further common
 problems.



https://packagist.org/packages/creocoder/yii2-nested-set-behavior