Adapt BindableService in ServerBuilder#addService

Makes binding services to server as simple as it can get.
diff --git a/compiler/src/testNano/golden/TestService.java.txt b/compiler/src/testNano/golden/TestService.java.txt
index 3aacbf8..0be68b1 100644
--- a/compiler/src/testNano/golden/TestService.java.txt
+++ b/compiler/src/testNano/golden/TestService.java.txt
@@ -302,7 +302,7 @@
     }
   }
 
-  public static abstract class AbstractTestService implements TestService, io.grpc.stub.BindableService {
+  public static abstract class AbstractTestService implements TestService, io.grpc.BindableService {
     @Override public io.grpc.ServerServiceDefinition bindService() {
       return TestServiceGrpc.bindService(this);
     }