Upgrade parent from 2.2.1 to 2.3.1.

Author: sutra

pom.xml

@@ -9,7 +9,7 @@
     <parent>
         <groupId>org.oxerr</groupId>
         <artifactId>oxerr-parent</artifactId>
-        <version>2.2.1</version>
+        <version>2.3.1</version>
         <relativePath /> <!-- lookup parent from repository -->
     </parent>
     <groupId>us.codecraft</groupId>