why on tutorial yet use React.createClass and not React.Component? see:
facebook.github.io/react/docs/tutorial.html
must everybody abandon React.createaClass
from official doc: https://facebook.github.io/react/blog/2015/03/10/react-v0.13.html
"Our eventual goal is for ES6 classes to replace React.createClass completely, but until we have a replacement for current mixin use cases and support for class property initializers in the language, we don't plan to deprecate React.createClass.""