Example for using with create-react-app

BUG: The class names generated start with numbers and class names starting with numbers are not accepted

This is not exactly a BUG but an addition to the docs on how to use it with [create-react-app](https://github.com/facebook/create-react-app) will be amazingly helpful. Although it needs ejecting it would be great.

I had to pull out:
```js
root.walkRules(rule => {
if (!rule.selectors) {
return rule;
}
rule.selectors = rule.selectors.map(
obfuscateClassNames.obfuscateClassNamesInSelector({
seed: "app"
})
);
});
```
An write my own `postcss -loader` plugin to get the obfuscation to work. But when building I get the error `Failed to minify the code from this file: ./node_modules/react-armor/dist/node/prod/lib/transformClassNames.js:17`

After fixing the import like `import obfuscateClassNames from "react-armor/dist/node/prod/lib/obfuscateClassNames";` I now get an error saying `Failed to minify the code from this file: ./node_modules/react-traverse/dist/node/prod/lib/traverse.js:43`.

Managed to get it working. But its not great about how I did it. I think integration should be easier

Also can you consider recompile and public your package as ES5 to npm