reads for the UI: TotalCoins, Lives, IsRunOver, CurrentLevel,
LevelOf/IsOwned/CanAfford, HasCleared. The read half of candidate 01 -
callers get a narrow surface instead of reaching into state.
new domain events LivesChanged / TotalCoinsChanged / SkillSetChanged,
announced by comparing against the last announced value, so an operation
can neither forget to announce nor announce something unchanged.
HandlePlayerDeath now clears the spent attempt - it was still counting
towards TotalCoins after its ledger had been discarded.
republisher and EventBus extended; SkillSetChanged is what SkillManager
will reconcile against instead of the non-atomic call pairs. 65 tests.
Gabriel Kaszewski
ca54bf0f82