Make contracts import path-independent from the caller

Author: rht

agents/metainsuranceorg.py

@@ -3,8 +3,7 @@
 import numpy as np
 import scipy.stats
 import copy
-from contracts.insurancecontract import InsuranceContract
-from contracts.reinsurancecontract import ReinsuranceContract
+from contracts import InsuranceContract, ReinsuranceContract
 from riskmodel import RiskModel
 import sys, pdb
 import uuid

contracts/__init__.py

@@ -0,0 +1,2 @@
+from .insurancecontract import InsuranceContract
+from .reinsurancecontract import ReinsuranceContract