Update to Powermock 1.6.6

Closes gh-602

Author: jzheaux

gradle/java.gradle

@@ -19,7 +19,7 @@ ext.log4jVersion = '1.2.17'
 ext.mockitoVersion = '1.10.19'
 ext.queryDslVersion = '4.0.9'
 ext.slf4jVersion = '1.7.32'
-ext.powerMockVersion = '1.6.5'
+ext.powerMockVersion = '1.6.6'
 ext.commonsPool2Version = '2.4.2'
 ext.assertjVersion= '2.3.0'
 ext.hibernateVersion = '5.2.5.Final'