unrecognized tag in pom xml

You have to surround the plugins tag with the build tag like this: 

  <build>
    <plugins>
     <plugin>
      ...
     </plugin>
    </plugins>
  </build>

or with the build and pluginManagement tags like this:

  <build>
    <pluginManagement>
      <plugins> 
       <plugin>
        ...
       </plugin>
      </plugins>
    </pluginManagement>
  </build>