examples: add bazel build example

## Bazel

If you prefer to use Bazel:
```
(With Bazel v0.4.5 or above.)
$ bazel build :hello-world-server :hello-world-client
$ # Run the server:
$ bazel-bin/hello-world-server
$ # In another terminal run the client
$ bazel-bin/hello-world-client
```
diff --git a/.gitignore b/.gitignore
index 7c8b732..0858b49 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@
 
 # Bazel
 bazel-bin
+bazel-examples
 bazel-genfiles
 bazel-grpc-java
 bazel-out