React-SDK - 2.0.0

## [2.0.0] - April 30th, 2020

Upgrade `@optimizely/optimizely-sdk` to 4.0.0. See [@optimizely/optimizely-sdk Release 4.0.0](https://github.com/optimizely/javascript-sdk/releases/tag/v4.0.0) for more details.

### Breaking Changes

- Changed supported React version to 16.8+

- @optimizely/optimizely-sdk no longer adds `Promise` polyfill in its browser entry point

- Dropped support for Node.js version <8

### New Features

- Refactored `` to a functional component that uses the `useFeature` hook under the hood. See [#32](https://github.com/optimizely/react-sdk/pull/32) for more details.

- Refactored `` to a functional component that uses the `useExperiment` hook under the hood. See [#36](https://github.com/optimizely/react-sdk/pull/36) for more details.

- Added `useExperiment` hook

- Can be used to retrieve the variation for an experiment. See [#36](https://github.com/optimizely/react-sdk/pull/36) for more details.

- Added `useFeature` hook
- Can be used to retrieve the status of a feature flag and its variables. See [#28](https://github.com/optimizely/react-sdk/pull/28) for more details.

- Removed lodash dependency

### Enhancements

- Exposed the entire context object used by ``.
- Enables support for using APIs which require passing reference to a context object, like `useContext`. [#27](https://github.com/optimizely/react-sdk/pull/27) for more details.


https://github.com/optimizely/react-sdk/releases/tag/2.0.0