Correctly parse multiple resources from files

Refactored how files, directories and stdin are handled. Every file must pass
through the FileVisitor and then streamed through StreamVisitor. FileVisitor
takes care of opening/closing files and StreamVisitor is parsing multiple
resources.

examples/examples_test.go

@@ -200,6 +200,7 @@ func TestExampleObjectSchemas(t *testing.T) {
 			"http-liveness": &api.Pod{},
 		},
 		"../examples": {
+			"multi-pod":               nil,
 			"pod":                     &api.Pod{},
 			"replication":             &api.ReplicationController{},
 			"scheduler-policy-config": &schedulerapi.Policy{},