First commit of game project

Did a few solid hours of TDD last night to get the bare bones of the game in place. So far there's adding/removing towers, and the logic for monsters entering/leaving tiles. That includes the Goal tile, and there's a GameOver event fired when the Goal runs out of points.

The way I imagined monster movement working last night was: every time they move a certain distance they fire a MonsterMoved event. The World is listening for these events. When it detects that a monster has moved over a tile boundary, it fires a MonsterChangedTile event. All the tiles are listening for these, and it allows them to keep a list of monsters they contain (especially important for the Goal tile).

This initially seemed wasteful to me - it's a lot of events - but then I thought "computers are fast as fuck", and ignored myself. I'd like to use the philosophy of naive implementation, only optimising where it's painfully obvious or actually costing us CPU.

(Thinking about it now, World should know which tile the monster has moved into, and message it directly - ah well, the events haven't actually been implemented yet so it's an easy change.)

Doing the tests first was pretty helpful - your code starts off being useable - it has to be so you can test it. It does seem quite slow going at first, but you have a certain level of confidence in your code afterwards that you don't get otherwise. Definitely recommend you guys give it a shot. Give me a shout if you need a hand with the mocking framework or the minutiae of NUnit.