Move more code into separate classes

It might make logical sense.  Honestly, I'm just tired of the code for
World being so long.

aoe/housing.py

@@ -1,12 +1,22 @@
 from collections import defaultdict
 
 from aoe.types import *
+from aoe.exceptions import *
 
 
 
 class Housing():
 
 
+    def check_housing(self, world, thing):
+        required = self.required[thing]
+
+        if required > 0:
+            pop_space = world.get_population_space()
+            if world.get_effective_population() > pop_space + required:
+                raise YallGotHousedException
+
+
     def __init__(self):
         self.space = defaultdict(int, {
                       Buildings.HOUSE: 5,