Use each-async / Update dependencies and devDependencies

* [each-async](https://github.com/sindresorhus/each-async) is an async iteration module, like [`async.each`](https://github.com/caolan/async#each). It is smaller and loaded faster than [async](https://github.com/caolan/async). We don't need to load large `async` module only for `async.each`.
* I updated dependencies and devDependencies.