Make sure bootstrap sources are ordered before use.

Make call to sort() before setting on builder.sources().

fixes gh-176

(cherry picked from commit 6dc35d1)

spring-cloud-context/src/main/java/org/springframework/cloud/bootstrap/BootstrapApplicationListener.java

@@ -133,8 +133,8 @@ public class BootstrapApplicationListener
 			}
 			sources.add(cls);
 		}
-		builder.sources(sources.toArray(new Class[sources.size()]));
 		AnnotationAwareOrderComparator.sort(sources);
+		builder.sources(sources.toArray(new Class[sources.size()]));
 		final ConfigurableApplicationContext context = builder.run();
 		// Make the bootstrap context a parent of the app context
 		addAncestorInitializer(application, context);