Game#play output turn number
Default invention probability = 2%
Implement the main-loop/sub-loop described in 3.4

Appearantly I did not get the main loop algorithm correct.
This is from Kirby 2000 chapter 3.4:

1) Select random position in population array.
2) Replace player at that position with a newbie.
3) Repeat (sub-loop):
3a) Choose one of the newbie's neighbors.
3b) The neighbor speaks and only the newbie learns.

Set default iterations count to 5000 (as in paper).
Default sub-iterations count is 100 (same).

This fixes #3.