Update walkthrough code to use yarn instead of npm (#671)

docs/00 Quick Start/Testing.md

@@ -7,7 +7,7 @@ React DnD is test-friendly. The whole drag and drop interaction, including the r
 
 There are several different approaches to testing React components. React DnD is not opinionated and lets you use either of them. **Neither of those approaches require the browser event system to be available.**
 
-A few test examples are included with the React DnD inside its `examples` folder. Run `npm install` and `npm test` inside the `react-dnd` root folder to start them.
+A few test examples are included with the React DnD inside its `examples` folder. Run `yarn install` and `yarn test` inside the `react-dnd` root folder to start them.
 
 ### Testing the Components in Isolation
 

examples/README.md

@@ -1,3 +1,3 @@
 The examples are written using [ES7](http://react-dnd.github.io/react-dnd/docs-faq.html#what-is-the-syntax-i-see-in-the-es7-code-examples-) and use [decorators](https://github.com/wycats/javascript-decorators). You don't have to use the decorators for React DnD, they are completely optional. [The tutorial](http://react-dnd.github.io/react-dnd/docs-tutorial.html) should give you a good idea about using React DnD in ES5, ES6, or ES7.
 
-Check out the [hosted versions of this examples](http://react-dnd.github.io/react-dnd/examples-chessboard-tutorial-app.html). To run them locally, clone the repo, and run `npm install && npm start`. It will take a while to start, but after the site is built, you can access the examples by opening [http://localhost:8080/](http://localhost:8080/) and clicking “Examples” in the navigation bar.
+Check out the [hosted versions of this examples](http://react-dnd.github.io/react-dnd/examples-chessboard-tutorial-app.html). To run them locally, clone the repo, and run `yarn install && yarn start`. It will take a while to start, but after the site is built, you can access the examples by opening [http://localhost:8080/](http://localhost:8080/) and clicking “Examples” in the navigation bar.

site/README.md

@@ -5,8 +5,8 @@ View it on the web: http://react-dnd.github.io/react-dnd
 Run it locally:
 
 ```
-npm install
-npm start
+yarn install
+yarn start
 ```
 
 After it builds the static site (might take about half a minute), open http://localhost:8080/.