Add type hints to mock-player

[janga1997]

@marcharper @drvinceknight
Fixes part of #808

1. Is the paramter actions just a list of actions? That is List[axelrod.actions.Action]?

2. I still don't understand what history is. I know it is a list, but of what I don't know.

3. And I think the type of state_dist is collections.defaultdict.

[marcharper]

History is a list of actions, same for actions. state_dist a defaultdict (of int but I'm not sure if you can test that).

[janga1997]

So history has the same type of actions. Okay
For state_dist should I just keep the type as collections.defaultdict?

[marcharper]

Yeah I think just a defaultdict.

[marcharper]

This one typechecks so far. I'll run the checker again after you make updates for the types you asked about.

[marcharper]

Just __init__ -> None for this one and then I think it's good.