Merge pull request FirefoxUX#38 from FirefoxUX/readme-fixes

Readme fixes

README.md

@@ -2,7 +2,23 @@
 
 [![CircleCI](https://circleci.com/gh/FirefoxUX/photon-components-web.svg?style=svg)](https://circleci.com/gh/FirefoxUX/photon-components-web)
 
-Photon versions of the some common web UI components
+This repository contains CSS styles and some React components to replicate the standard styles used in Firefox. The most recent style guidelines for Firefox are called "Photon" (hence the name of this repository).
+
+These components are intended to be used anywhere where you want to make an HTML interface appear to be part of the browser itself. Examples where this might be useful include add-ons/extensions, UI directly in Firefox that is implemented in HTML, and some Mozilla properties like addons.mozilla.org.
+
+This repository is not intended for a general audience. You do not have to use React to make use of the styles.
+
+## Development
+
+To get started:
+
+```sh
+npm install
+# To generate static CSS and images/ in dist/ :
+npm run build:webpack
+# To run the demonstration site locally on http://localhost:9001/ :
+npm start
+```
 
 ## Conventions