Switch to openjdk8

Repair Travis build

Merge pull request spring-petclinic#111 from arey/feature/duplicateConf

Remove configuration hosted by the Config Server

Merge pull request spring-petclinic#83 from spring-petclinic/feature/…

…Finchley

Upgrade to Spring Cloud Finchley spring-petclinic#72

Reduce memory consumption of Docker images spring-petclinic#76 (sprin…

…g-petclinic#77)

* Reduce memory consumption of Docker images spring-petclinic#76

The fix switches from an outdated Oracle Java 8 Docker image
to the current openjdk:8 image. The Java VM of this image
supports the parameters to make the Java VM Docker aware.
With this option it becomes possible to set the memory
limit to 256MB which reduces the memory consumption by
75% and leaves the application still operational.

* Added a NOTE about the Docker VM resource usage on Mac and Win

This closes spring-petclinic#76 and hopefully improves the first time user-experience
of the Docker compose way of running the demo microservices.