update the readme to convert newton ==> playfair

packages/playfair/README.md

-# Newton
-[![Build Status](https://travis-ci.org/domokit/newton.svg?branch=master)](https://travis-ci.org/domokit/newton)
-[![Coverage Status](https://coveralls.io/repos/domokit/newton/badge.svg?branch=master)](https://coveralls.io/r/domokit/newton?branch=master)
+# playfair
+[![Build Status](https://travis-ci.org/domokit/playfair.svg?branch=master)](https://travis-ci.org/domokit/playfair)
+[![Coverage Status](https://coveralls.io/repos/domokit/playfair/badge.svg?branch=master)](https://coveralls.io/r/domokit/playfair?branch=master)
 
-Simple Physics Simulations for Dart. Springs, friction, gravity, etc.
+A simple charting library for Sky.

packages/playfair/pubspec.yaml

 name: playfair
-description: Simple Charting Library for Sky
+description: A simple charting library for Sky
 version: 0.0.1
 author: Chromium Authors <sky-dev@googlegroups.com>
 homepage: https://github.com/domokit/playfair