Force the connections in wiremock tests to be closed.
See https://github.com/tomakehurst/wiremock/issues/485

It turns out that imho when talking about application groups (identified
by name) and application instances it's just logical to speak of
instances and applications. So the Application class get's renamed to
Instance. So an Application is now a set of Instances with the same name

Update to Spring Cloud Brixton and add the concept of ServiceInstanceConverters.
A ServiceConverter is used to convert discovered ServiceInstances to
Applications. The old converter and one for Eureka is provided. It is also
possible to provide your own implementation.

closes #154