docs: Update stackdriver examples for tracing and stats (#613)

* docs: Update stackdriver examples for tracing and stats

* update based on review

Author: mutianf

README.md

@@ -203,7 +203,7 @@ try {
 
 TIP: If you are experiencing version conflicts with gRPC, see [Version Conflicts](#version-conflicts).
 
-## OpenCensus Tracing
+## Client request tracing: OpenCensus Tracing
 
 Cloud Bigtable client supports [OpenCensus Tracing](https://opencensus.io/tracing/),
 which gives insight into the client internals and aids in debugging production issues.
@@ -258,6 +258,8 @@ StackdriverTraceExporter.createAndRegister(
       .setProjectId("YOUR_PROJECT_ID")
       .build());
 ```
+You can view the traces on the Google Cloud Platform Console 
+[Trace](https://console.cloud.google.com/traces) page.
 
 By default traces are [sampled](https://opencensus.io/tracing/sampling) at a rate of about 1/10,000.
 You can configure a higher rate by updating the active tracing params:
@@ -273,7 +275,7 @@ Tracing.getTraceConfig().updateActiveTraceParams(
 );
 ```
 
-## OpenCensus Stats
+## Enabling Cloud Bigtable Metrics: OpenCensus Stats
 
 Cloud Bigtable client supports [Opencensus Metrics](https://opencensus.io/stats/),
 which gives insight into the client internals and aids in debugging production issues.
@@ -376,6 +378,34 @@ BigtableDataSettings.enableOpenCensusStats();
 BigtableDataSettings.enableGfeOpenCensusStats();
 ```
 
+You can view the metrics on the Google Cloud Platform Console
+[Metrics explorer](https://console.cloud.google.com/monitoring/metrics-explorer)
+page.
+
+You can configure how frequently metrics are pushed to StackDriver and the
+[Monitored resource type](https://cloud.google.com/monitoring/api/resources) by
+updating `StackdriverStatsConfiguration`:
+
+``` java
+// Example: configuring export interval and monitored resource type
+StackdriverStatsExporter.createAndRegister(
+    StackdriverStatsConfiguration.builder()
+        .setProjectId("YOUR_PROJECT_ID")
+        // Exporting metrics every 10 seconds
+        .setExportInterval(Duration.create(10, 0))
+        // Configure monitored resource type. A common practice is to use the
+        // monitored resource objects that represent the physical resources
+        // where your application code is running. See the full list of
+        // monitored resource type here:
+        // https://cloud.google.com/monitoring/api/resources
+        .setMonitoredResource(MonitoredResource.newBuilder()
+             .setType("global")
+             .putLabels("project_id", "YOUR_PROJECT_ID")
+           .build())
+        .build()
+);
+```
+
 ## Version Conflicts
 
 google-cloud-bigtable depends on gRPC directly which may conflict with the versions brought