fix typo setupTest.js -> setupTests.js (#555)

Author: ippa

CHANGELOG.md

@@ -4,15 +4,15 @@
 
 * **Breaking Change:** Disabled implicit serving of source files in development. ([@gaearon](https://github.com/gaearon) in [#551](https://github.com/facebookincubator/create-react-app/pull/551))
 * You can use `NODE_PATH` environment variable for absolute `import` paths. ([@jimmyhmiller](https://github.com/jimmyhmiller) in [#476](https://github.com/facebookincubator/create-react-app/pull/476))
-* If `src/setupTest.js` exists, it will be used to setup the test environment. ([@gaelduplessix](https://github.com/gaelduplessix) in [#548](https://github.com/facebookincubator/create-react-app/pull/548))
+* If `src/setupTests.js` exists, it will be used to setup the test environment. ([@gaelduplessix](https://github.com/gaelduplessix) in [#548](https://github.com/facebookincubator/create-react-app/pull/548))
 * If `HTTPS` environment variable is set to `true`, development server will run in HTTPS mode. ([@dceddia](https://github.com/dceddia) in [#552](https://github.com/facebookincubator/create-react-app/pull/552))
 
 ### Migrating from 0.3.1 to 0.4.0
 
 Inside any created project that has not been ejected, run:
 
 ```
-npm install --save-dev --save-exact react-scripts@0.4.0
+npm install --save-dev --save-exact react-scripts@0.3.1
 ```
 
 ### Breaking Change in 0.4.0