Fix deprecation warnings - Update to React 15.6.2

[abarriel]

React.PropTypes, react-addons-test-utils, and react-addons-pure-render-mixin are depracted. To avoid any future complications, here are the new changes:

• Removed React.PropTypes for PropTypes, a separate package, use a codemods from react-codemods lib for applying those changes. Unique name of PropTypes object imported to have a generics code over the lib ( removed { T } in favor to { PropTypes } )

• Removed react-addons-test-utils deprecated since 15.5 after 15.5 react-dom/utils can be used, for shallow rendering react-test-render is use since after 15.5

• Update Package React and React Dom

• Removed react-addons-pure-render-mixin, we not longer use this addons, React.pureComponent provide exactly the same shouldComponentUpdate(with a shallowCompare) as PureRender did before. To match these changes along the lib, we add a new comparator ( which return true if the component is a React.Component or React.PureComponent ), because in the previous version react-nexus didn't have any information about PureComponent imported from React.

• Remove should from dependencies, it was imported twice on in devdependencies and dependencies

[eTorAken]

Also "Remove should from dependencies" in your commit message. Please explain why.

[abarriel]

This PR should be clean. I apply some changes