Started to investigate astropy#568. @johannesulf - this commit is my …

…first attempt to eliminate obvious sources of the memory leak.

halotools/empirical_models/factories/hod_mock_factory.py

@@ -159,10 +159,13 @@ def preprocess_halo_catalog(self, halocat):
         self._orig_halo_table = Table()
         for key in self.additional_haloprops:
             try:
-                self._orig_halo_table[key] = halo_table[key][:]
+                # self._orig_halo_table[key] = halo_table[key][:]
+                self._orig_halo_table[key] = np.copy(halo_table[key])
             except KeyError:
                 raise HalotoolsError(unavailable_haloprop_msg % key)
 
+        del halo_table
+
         self.model.build_lookup_tables()
 
     def populate(self, **kwargs):
@@ -319,7 +322,10 @@ def allocate_memory(self):
         ``_occupation`` and ``_gal_type_indices``.
 
         """
-
+        try:
+            del self.galaxy_table
+        except AttributeError:
+            pass
         self.galaxy_table = Table()
 
         # We will keep track of the calling sequence with a list called _remaining_methods_to_call