README Polishing
README Polishing

This change polishes up the README by adding a note about initializing the
dropsonde submodule.

Orange-OpenSource/cf-java-client,orange-cloudfoundry/cf-java-client,cloudfoundry/cf-java-client,cloudfoundry/cf-java-client,Orange-OpenSource/cf-java-client,cloudfoundry/cf-java-client,orange-cloudfoundry/cf-java-client,alexander071/cf-java-client,alexander071/cf-java-client