docker-maven-plugin issue

[ahar-zz]

Hi @carnellj ,

there is a problem when you try to docker:build code from spmia-chapter3 repository.
The problem is well described here:
spotify/dockerfile-maven#90

Please, consider adding

             <dependencies>
                 <dependency>
                     <groupId>javax.activation</groupId>
                     <artifactId>activation</artifactId>
                     <version>1.1.1</version>
                 </dependency>
             </dependencies>

To the docker-maven-plugin dependencies.

Thank you.