add Actor class with hit-points and other attributes

[barrybecker4]

There are many improvements that I will leave as an exercise for reader (Brian I hope).
Next to each is a number which is the number of hours I expect it would take me to implement.

1. Keep track of the items that the player has. They initially start with about 10 things but then find/use
   items as their adventure progresses.
2. Automatic fighting with monsters. We know the hit points and armor class of the player and monster.
   It should be a simple matter to have the combat automatically carried out in order to determine the winner and subtract hit point losses as appropriate. We can also take into other effects like disease or healing effects. The player should also be given the option to flee, or instigate other action during the melee.
3. Add a graphical User Interface. We could have windows that pop up to show the players stats or item inventory.
4. Make multi-player (hard)
5. Have probabilistic choices. For example, if you encounter a monster and choose to fight it, then
   the outcome may be one of several different things. We can also influence the outcome by what sort of
   items the player has.