Upgrade extra-enforcer-rules 1.4 -> 1.5.1 (#88)

See:
- https://github.com/mojohaus/extra-enforcer-rules/releases/tag/extra-enforcer-rules-1.5.0
- https://github.com/mojohaus/extra-enforcer-rules/releases/tag/extra-enforcer-rules-1.5.1
- mojohaus/extra-enforcer-rules@extra-enforcer-rules-1.4...extra-enforcer-rules-1.5.1

pom.xml

@@ -810,7 +810,7 @@
                         <dependency>
                             <groupId>org.codehaus.mojo</groupId>
                             <artifactId>extra-enforcer-rules</artifactId>
-                            <version>1.4</version>
+                            <version>1.5.1</version>
                         </dependency>
                     </dependencies>
                     <executions>