Update documentation and diagnostics for the gRPC example. (#84)

* Quote IP on the command line in instructions.

* Report an error message when not exporting a view due to a changed descriptor.

Author: Ian Sturdy

examples/grpc/README.md

@@ -22,7 +22,7 @@ To increase gRPC verbosity, try:
 
 ```shell
 env GRPC_VERBOSITY=DEBUG ../../bazel-bin/examples/grpc/hello_server 9001
-env GRPC_VERBOSITY=DEBUG ../../bazel-bin/examples/grpc/hello_client [::]:9001
+env GRPC_VERBOSITY=DEBUG ../../bazel-bin/examples/grpc/hello_client "[::]:9001"
 ```
 
 ## Stackdriver

opencensus/exporters/stats/stackdriver/internal/stackdriver_exporter.cc

@@ -118,7 +118,13 @@ bool StackdriverExporter::Handler::MaybeRegisterView(
     const opencensus::stats::ViewDescriptor& descriptor) {
   const auto& it = registered_descriptors_.find(descriptor.name());
   if (it != registered_descriptors_.end()) {
-    return it->second == descriptor;
+    if (it->second != descriptor) {
+      std::cerr << "Not exporting altered view: " << descriptor.DebugString()
+                << "\nAlready registered as: " << it->second.DebugString()
+                << "\n";
+      return false;
+    }
+    return true;
   }
 
   auto request = google::monitoring::v3::CreateMetricDescriptorRequest();