Be aware that the source code of the book is under development.
https://code.google.com/p/activitiinaction/
The code is upgraded to version 5.12 or 5.13 of Activiti. I'll make sure it gets upgraded to 5.14 soon. So you can update to the latest book code from this Google code repository.
For now you have two options, either work with an older version of Activiti or change the Activiti version in the pom.xml file of the book source code.
Best regards,
Tijs