merge in master

also clean up unused canary values

This will allow third party apps to use these in their code

* export Context instead of just Consumer/Provider
* fix error messages for removed functionality
* minor displayName change

when the time is right, one need only
change the BABEL_ENV for build:umd:min back to "rollup-production"

* React.forwardRef is VERY slow, on the order of 2x slower in our benchmark. So we only enable it if withRef="forwardRef" folks using withRef=true will get an error telling them to update and not rely on getWrappedInstance() but just to use the ref directly
* renderCountProp is removed, as this is natively supported in React dev tools now
* all usages of shallowEquals are removed for pure components, it was unnecessary.
* instead of allowing passing in a custom Context consumer in props, it is now required to be passed in via connect options at declaration time.