Update react in / from 16.4.0 to 16.7.0

[dependencies]

Dependencies.io has updated react (a npm dependency in /) from "16.4.0" to "16.7.0".

16.7.0

React DOM

• Fix performance of React.lazy for large numbers of lazily-loaded components. (acdlite in #14429)
• Clear fields on unmount to avoid memory leaks. (trueadm in #14276)
• Fix bug with SSR and context when mixing react-dom/server@16.6 and react@<16.6. (gaearon in #14291)
• Fix a performance regression in profiling mode. (bvaughn in #14383)

Scheduler (Experimental)

• Post to MessageChannel instead of window. (acdlite in #14234)
• Reduce serialization overhead. (developit in #14249)
• Fix fallback to setTimeout in testing environments. (bvaughn in #14358)
• Add methods for debugging. (mrkev in #14053)