Change unit-test syntax to be pytest compatible

Author: timstaley

skrules/tests/test_common.py

@@ -4,8 +4,8 @@
 
 
 def test_classifier():
-    return check_estimator(SkopeRules)
+    check_estimator(SkopeRules)
 
 
 def test_load_credit_data():
-    return load_credit_data().data.shape[0] == 30000
+    assert load_credit_data().data.shape[0] == 30000