Delete Step_2.md

Remove separate step now that all the content has been moved into the main doc

Step_2.md

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-# Step-2: Write a service client.
-
-This step uses the generated code to write a simple client to access the hello
-service. The full client is in [GreetingsClient.java](src/main/java/ex/grpc/GreetingsClient.java).
-
-
-## Configuring the service to connect to.
-
-The client contains uses a Stub to contact the service. The internet address
-is configured in the client constructor. gRPC Channel is the abstraction over
-transport handling; its constructor accepts the host name and port of the
-service. The channel in turn is used to construct the Stub.
-
-
-```
-  private final ChannelImpl channel;
-  private final GreetingGrpc.GreetingBlockingStub blockingStub;
-
-  public HelloClient(String host, int port) {
-    channel = NettyChannelBuilder.forAddress(host, port)
-              .negotiationType(NegotiationType.PLAINTEXT)
-              .build();
-    blockingStub = GreetingGrpc.newBlockingStub(channel);
-  }
-
-```
-
-## Obtaining a greeting
-
-The greet method uses the stub to contact the service and obtain a greeting.
-It:
-- constructs a request
-- obtains a reply from the stub
-- prints out the greeting
-
-
-```
-  public void greet(String name) {
-    logger.debug("Will try to greet " + name + " ...");
-    try {
-      Helloworld.HelloRequest request = Helloworld.HelloRequest.newBuilder().setName(name).build();
-      Helloworld.HelloReply reply = blockingStub.hello(request);
-      logger.info("Greeting: " + reply.getMessage());
-    } catch (RuntimeException e) {
-      logger.log(Level.WARNING, "RPC failed", e);
-      return;
-    }
-  }
-
-```
-
-## Running from the command line
-
-The main method puts together the example so that it can be run from a command
-line.
-
-```
-    /* Access a service running on the local machine on port 50051 */
-    HelloClient client = new HelloClient("localhost", 50051);
-    String user = "world";
-    if (args.length > 1) {
-      user = args[1];
-    }
-    client.greet(user);
-
-```
-
-It can be built as follows.
-
-```
-$ mvn package
-```
-
-It can also be run, but doing so now would end up a with a failure as there is
-no server available yet.  The [next step](Step_3.md), describes how to
-implement, build and run a server that supports the service description.
-
-## Notes
-
-- The client uses a blocking stub. This means that the RPC call waits for the
-  server to respond, and will either return a response or raise an exception.
-
-- gRPC Java has other kinds of stubs that make non-blocking calls to the
-  server, where the response is returned asynchronously.  Usage of these stubs
-  is a more advanced topic and will be described in later steps.