ES2015 arrow function not transpiled

[enoh-barbu]

I don't know if this is a babel issue or you should use functions instead of arrow functions because I get an error on old browsers that don't support the new syntax: SyntaxError: Unexpected token '>'

as well const declarations

[SamVerschueren]

We aim for Node.js, not the browser. You can find a more detailed explanation here sindresorhus/ama#446.

If you use Webpack, check out babel-engine-plugin, which transpiles only the dependencies that needs to be transpiled.