fix android app build broken by 3666de4427

In grpc-java, io.grpc.nano was renamed to io.grpc.protobuf.nano.
Therefore, android app fails to build with the latest version of grpc-java.

java/android/app/build.gradle

@@ -28,7 +28,7 @@ dependencies {
     // You need to build the https://github.com/grpc/grpc-java
     // to obtain these libraries below.
     compile 'io.grpc:grpc-core:0.1.0-SNAPSHOT'
-    compile 'io.grpc:grpc-nano:0.1.0-SNAPSHOT'
+    compile 'io.grpc:grpc-protobuf-nano:0.1.0-SNAPSHOT'
     compile 'io.grpc:grpc-okhttp:0.1.0-SNAPSHOT'
     compile 'io.grpc:grpc-stub:0.1.0-SNAPSHOT'
 }

java/android/app/src/main/java/io/grpc/helloworldexample/GreeterGrpc.java

@@ -15,15 +15,15 @@ public class GreeterGrpc {
             Helloworld.HelloReply> METHOD_SAY_HELLO =
             io.grpc.stub.Method.create(
                     io.grpc.MethodType.UNARY, "SayHello",
-                    io.grpc.nano.NanoUtils.<Helloworld.HelloRequest>marshaller(
-                            new io.grpc.nano.Parser<Helloworld.HelloRequest>() {
+                    io.grpc.protobuf.nano.NanoUtils.<Helloworld.HelloRequest>marshaller(
+                            new io.grpc.protobuf.nano.Parser<Helloworld.HelloRequest>() {
                                 @Override
                                 public Helloworld.HelloRequest parse(com.google.protobuf.nano.CodedInputByteBufferNano input) throws IOException {
                                     return Helloworld.HelloRequest.parseFrom(input);
                                 }
                             }),
-                    io.grpc.nano.NanoUtils.<Helloworld.HelloReply>marshaller(
-                            new io.grpc.nano.Parser<Helloworld.HelloReply>() {
+                    io.grpc.protobuf.nano.NanoUtils.<Helloworld.HelloReply>marshaller(
+                            new io.grpc.protobuf.nano.Parser<Helloworld.HelloReply>() {
                                 @Override
                                 public Helloworld.HelloReply parse(com.google.protobuf.nano.CodedInputByteBufferNano input) throws IOException {
                                     return Helloworld.HelloReply.parseFrom(input);