Update react in / from 16.4.0 to 16.6.0

[dependencies]

Dependencies.io has updated react (a npm dependency in /) from "16.4.0" to "16.6.0".

16.6.0

React

• Add React.memo() as an alternative to PureComponent for functions. (acdlite in #13748)
• Add React.lazy() for code splitting components. (acdlite in #13885)
• React.StrictMode now warns about legacy context API. (bvaughn in #13760)
• React.StrictMode now warns about findDOMNode. (sebmarkbage in #13841)
• Rename unstable_AsyncMode to unstable_ConcurrentMode. (trueadm in #13732)
• Rename unstable_Placeholder to Suspense, and delayMs to maxDuration. (gaearon in #13799 and sebmarkbage in #13922)

React DOM

• Add contextType as a more ergonomic way to subscribe to context from a class. (bvaughn in #13728)
• Add getDerivedStateFromError lifecycle method for catching errors in a future asynchronous server-side renderer. (bvaughn in #13746)
• Warn when <Context> is used instead of <Context.Consumer>. (trueadm in #13829)
• Fix gray overlay on iOS Safari. (philipp-spiess in #13778)
• Fix a bug caused by overwriting window.event in development. (sergei-startsev in #13697)

React DOM Server

• Add support for React.memo(). (alexmckenley in #13855)
• Add support for contextType. (alexmckenley and sebmarkbage in #13889)

Scheduler (Experimental)

• Rename the package to scheduler. (gaearon in #13683)
• Support priority levels, continuations, and wrapped callbacks. (acdlite in #13720 and #13842)
• Improve the fallback mechanism in non-DOM environments. (acdlite in #13740)
• Schedule requestAnimationFrame earlier. (acdlite in #13785)
• Fix the DOM detection to be more thorough. (trueadm in #13731)
• Fix bugs with interaction tracing. (bvaughn in #13590)
• Add the envify transform to the package. (mridgway in #13766)