Add arrow function based implementation

[dmitriz]

Supersedes #7

[dominictarr]

why rename console.log? I can expect the reader to already know what console.log does, so they can understand each line, but now I had to go figure out what show was. At first I thought it was a module.

[dmitriz]

It is a habit thing for me, to avoid hard-coding, so I can make change in single place, e.g. to turn it silent, and also get a better performance by not repeatedly looking up the props.
But if you feel repeating console.log would be more appropriate here, I'll happily change it.

[dmitriz]

Maybe I need to explain the motivations behind my PR because the changes themselves are trivial.

• I felt highly inspired by discovering the pull-streams as it really illustrates how things don't need to be bloated to be powerful :)

• It was my understanding that this project is educational that is worth catching people's attention. Which would be helped by a fresh, even trivial update, as people often look for the last update date.

• Right now the reader has to get through to the end for the only example.
  I've thought more examples illustrating each function might be helpful.
  But I wasn't sure about the intended scope of examples here.
  Too many examples are bloated with details not related to the phenomena they illustrate,
  while this file is nicely kept dead simple, which is not something I'd want to disturb :)