Attempt to move to create-react-context

[jaredpalmer]

This PR attempts to removes the direct use of prop-types and instead uses create-react-context.

Writing typed render prop components that take a generic is super awkward now. Ugh.

To make tests pass, we will need to either use enzyme mount / or figure out something else

[Dremora]

Any progress on this one? Right now our app has quite large form which takes up to 1 second to re-render on each key press, especially on mobile devices. We can't use PureComponent because Formik relies on the old context, and thus the components simply don't re-render. FastField is blocked by #560.

[jaredpalmer]

Will make a college try soon. My team is also upgrading to 16.3 this week

[jaredpalmer]

See #594 .

[jaredpalmer]

Any help finishing the move would be greatly appreciated.