Fix demo with maven 3

 - changed version of jetty-maven-plugin as 8.0.0.M1 seems to be a dud with maven 3.

- see http://stackoverflow.com/questions/4154238/jetty-maven-plugin-does-not-work-with-maven-3 for details

I found the above problem using Apache Maven 3.0.3 and java 7 on OSX
Updating to a newer version of the jetty-maven-plugin fixed the problem.