Upgraded to use the latest docker-java client

Hi,
First of all, thanks a lot for writing this plugin. This was a huge help for the task I am doing now. 

I have upgraded the docker-java client library and made some change into the plugin as well.  I have put some kind of hack in the StartMojo by adding Thread.sleep to make sure it gets enough time to start the container and the application. So far I have not come across anything which makes sure that application is up and running in the container.

Please review the code and let me know, if you want to make any change.
Regards,
Irfan