This moves the current fixture architecture to one based around create-react-app. There are a few important things to note:
* The react-loader.js script is always loaded before the bundle and will populate React and ReactDOM on the window. It is then read from the window by all components.
* The UI for the "React Sandbox" or "React Fixtures App" is also rendered with whatever version of React the user has selected. This means we dont have to deal with iframes or worry about multiple versions of React potentially interferring. But it also means that all components must be written using createClass to be fully backwards compatable. I tested back to 0.13.1 and it works fine.
* Add manual build fixtures
* Inject ReactDOM into ReactWithAddons from ReactWithAddons
We used to read ReactDOM as a global inside ReactAddonsDOMDependenciesUMDShim.
This didn't work in AMD environments such as RequireJS and SystemJS.
Instead, I changed it so that ReactDOM gets injected into ReactWithAddons by ReactDOM itself.
This way we don't have to try to require it (which wouldn't work because AMD doesn't handle circular dependencies well).
This means you have to load ReactDOM first before using ReactDOM-dependent addons, but this was already the case before.
This commit makes all build fixtures pass.
* Memoize ReactDOM to avoid going into require on every access
* Add Brunch fixture
* Inline requires to work around Brunch bug
See #8556 and https://github.com/brunch/brunch/issues/1591#issuecomment-270742503 for context.
This appears to be a Brunch bug but we can keep a temporary fix until the next major.