Update readme intro and add primer-css to package list

Author: broccolini

README.md

@@ -3,16 +3,17 @@
 [![NPM version](http://img.shields.io/npm/v/primer-css.svg)](https://www.npmjs.org/package/primer-css)
 [![Build Status](https://travis-ci.org/primer/primer-css.svg?branch=master)](https://travis-ci.org/primer/primer-css)
 
-> Primer is the CSS framework that powers GitHub's front-end design. It's purposefully limited to common components to provide our developers with the most flexibility, and to keep GitHub uniquely *GitHubby*. It's built with SCSS and available via NPM, so it's easy to include all or part of it within your own project.
+Primer is the CSS framework that powers GitHub's front-end design. Primer-css includes 23 packages that are grouped into 3 core meta-packages for easy install. Each package and meta-package is independently versioned and distributed via NPM, so it's easy to include all or part of Primer within your own project.
 
 ## Packages
 
-The Primer repo is managed as a monorepo that is composed of many npm packages.
+The Primer repo is managed as a monorepo that is composed of many NPM packages.
 
 ### Core Packages
 
 | Package | Version | Status |
 |---|---|---|
+| **[primer-css](/packages/primer-css)** <br />Includes all packages | [![npm](http://img.shields.io/npm/v/primer-css.svg)](https://www.npmjs.com/package/primer-css) |  [![Build Status](https://travis-ci.org/primer/primer-css.svg?branch=master)](https://travis-ci.org/primer/primer-css) |
 | [primer-core](/packages/primer-core) | [![npm](http://img.shields.io/npm/v/primer-core.svg)](https://www.npmjs.com/package/primer-core) |  [![Build Status](https://travis-ci.org/primer/primer-core.svg?branch=master)](https://travis-ci.org/primer/primer-core) |
 | [primer-product](/packages/primer-product) |  [![npm](http://img.shields.io/npm/v/primer-product.svg)](https://www.npmjs.com/package/primer-product) | [![Build Status](https://travis-ci.org/primer/primer-product.svg?branch=master)](https://travis-ci.org/primer/primer-product) |
 | [primer-marketing](/packages/primer-marketing) | [![npm](http://img.shields.io/npm/v/primer-marketing.svg)](https://www.npmjs.com/package/primer-marketing) | [![Build Status](https://travis-ci.org/primer/primer-marketing.svg?branch=master)](https://travis-ci.org/primer/primer-marketing) |