Merge lp://staging/~exarkun/game/getTerrain-on-pypy into lp://staging/game

This change fixes a test failure when the suite is run on PyPy:

```
[ERROR]
Traceback (most recent call last):
  File "/tmp/game/gam3/test/test_network.py", line 388, in test_getTerrain
    [args] = self.getCommands(SetTerrain)
exceptions.ValueError: expected length 1, got 0

gam3.test.test_network.NetworkTests.test_getTerrain
```

The cause is the difference in behavior of numpy on CPython vs PyPy when given float indexes. On CPython these are silently truncated to integers (the correct behavior in this case). On PyPy this usage is an error. Arguably this is a compatibility bug in PyPy's numpy - but using floats here is dumb and unintentional so it's worth fixing in Game anyway.