Add Iterant.dump method

[alexandru]

Observable has the .dump utility that we need for Iterant:

• API Documentation
• Source code: Observable.scala and DumpObservable

Signature:

sealed abstract class Iterant[F[_], A] {
  // ...
  def dump(prefix: String, out: PrintStream = System.out): Iterant[F, A]
}

Usage:

Iterant[Task].range(0, 4)
  .dump("O")
  .completeL.runAsync

What this does is to dump the incoming events to standard output, like so:

O --> 0
O --> 1
O --> 2
O --> 3
O completed

[Avasil]

I'd like to take this one as well :)

I see that in Observable it looks a bit different:

0: O-->0
1: O-->1
2: O-->2
3: O-->3
4: O completed

I feel like extra spaces are nicer but consistency might be more important unless we also update Observable and Observer?

[alexandru]

Ah, right, yeah, do the output like what we have with Observable, those index numbers are important, although you might add some spacing into Observable as well.

This is output meant for debugging, so people shouldn't have parsed that output anyway.

[alexandru]

@Avasil and yes, feel free to work on it.

[alexandru]

Solved in #439.