docs: add warning and update catalyst reference

Signed-off-by: Mike Murray <hellomikemurray@gmail.com>

Author: mikemurray

README.md

@@ -5,10 +5,12 @@
 
 ![Reaction Design System](https://blog.reactioncommerce.com/content/images/2018/09/style-guide-artwork.jpg)
 
+> ⚠️ Warning: This repository is in active development and is not ready for testing or usage.
+
 This is a single project with a package of commerce-focused React UI components and the code for the Reaction Design System website:
 
 - [`@reactioncommerce/catalyst`](https://www.npmjs.com/package/@reactioncommerce/catalyst): See the [package.json](https://github.com/reactioncommerce/catalyst/blob/master/package/package.json) in [`/package`](https://github.com/reactioncommerce/catalyst/tree/master/package) folder.
-- [Reaction Design System](https://designsystem.reactioncommerce.com/): See the root [package.json](https://github.com/reactioncommerce/catalyst/blob/master/package.json).
+- [Catalyst Components](https://catalyst.reactioncommerce.com/): See the root [package.json](https://github.com/reactioncommerce/catalyst/blob/master/package.json).
 
 We use the [React Styleguidist](https://react-styleguidist.js.org/) package to run and build the Reaction Design System website, and running the style guide locally doubles as an interactive playground for developing and testing the components.