Add support for Elixir exclusive types

[wende]

Need to find a way to make a type that would be more than what Elm has and would still be unique.
Types that needs to be covered:

• Pid
  • Use case: Incoming effects system
  • Caveats: Can't be matched on if not in tagged type. So probably has to be wrapped when received from outside. type Pid = Pid Int Int Int seems like the best option
• Module Atom (Can't be expressed using types)
  • Use case: Process naming (mostly)
  • Caveats: Has to be typed as string, less than elegant
• Ports (Not sure if essential)
• References (Not sure if essential - these are generally nothing else but side-effects )

[wende]

Closed. Won't be needed until #146 come through