* Add 0.4.2 changelog

* Update CHANGELOG.md

For the 0.4.0 CHANGELOG entry, the npm install command should be:
```
npm install --save-dev --save-exact react-scripts@0.4.0
```

Not:
```
npm install --save-dev --save-exact react-scripts@0.3.1
```

* Update CHANGELOG.md

* Update the changelog

* Update CHANGELOG.md