Examples not compatible with Elixir 1.10 or 1.11

[Shoowa]

What's the proper way to include either the Kaffe.Producer or Kaffe.Consumer into the children list. The examples from Elixir School and the README aren't satisfying the requirement to conform to the newer child specification.

[objectuser]

@Shoowa The README should be correct for Kaffe.GroupMemberSupervisor. Kaffe.Producer doesn't utilize a process so there's no need to include it in the children list.

We haven't yet updated the supervisors to support the newer child specification. I created a PR #69 but lost track of it at some point.

[Shoowa]

Thank you for the tip!