Update information in User Guide for Enzyme dependency (#1982)

Author: josephrace

packages/react-scripts/template/README.md

@@ -974,7 +974,7 @@ When you encounter bugs caused by changing components, you will gain a deeper in
 If you’d like to test components in isolation from the child components they render, we recommend using [`shallow()` rendering API](http://airbnb.io/enzyme/docs/api/shallow.html) from [Enzyme](http://airbnb.io/enzyme/). You can write a smoke test with it too:
 
 ```sh
-npm install --save-dev enzyme react-addons-test-utils
+npm install --save-dev enzyme react-test-renderer
 ```
 
 ```js
@@ -1518,17 +1518,17 @@ When you build the project, Create React App will place the `public` folder cont
 2. Install `serve` by running `npm install --save serve`.
 
 3. Add this line to `scripts` in `package.json`:
-    
+
     ```
     "now-start": "serve build/",
     ```
-    
+
 4. Run `now` from your project directory. You will see a **now.sh** URL in your output like this:
-    
+
     ```
     > Ready! https://your-project-dirname-tpspyhtdtk.now.sh (copied to clipboard)
     ```
-    
+
     Paste that URL into your browser when the build is complete, and you will see your deployed app.
 
 Details are available in [this article.](https://zeit.co/blog/now-static)