- include jail cards into trade

V implement income tax according to the rules. currently you always
  have to pay $200

V implement bankruptcy

V rents should not be payed before it's clear that the player has
  enough money

- introduce auctions by the bank (when a player refuses to buy an
  unowned property

and many more things (this list is incomplete)

0.3
===

V functional AI (stupid, without trading)
V framework for options: commands set and show
V option aifill, command aitoggle
