Only paginate queries by integer values

In order to avoid a bug where overlap page calculations could result
in requesting a fractional offset, coerce the value to an integer.

Change-Id: I22f9b444bf0965bf3146f3238a2afdf6d9860248

engagement/stats.py

@@ -384,7 +384,7 @@ def main(verbose=0):
             # Offset additional pages by half the returned entry count to help
             # avoid missing changes due to pagination instability
             if new_changes and new_changes[-1].get('_more_changes', False):
-                offset += len(new_changes)/2
+                offset += int(len(new_changes)/2)
             else:
                 offset = -1