message: Add --cxxopt=-std=c++11 to Tensorflow Android's Bazel instructions.
  Users have been reaching out on StackOverflow and bazel-discuss with a failed build due to incomplete instructions:
  https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/bazel-discuss/TPd2xeayFrY/PLA3frQuCAAJ
diff: @@ -52,6 +52,7 @@ Then, to build the native TF library:
  bazel build -c opt //tensorflow/contrib/android:libtensorflow_inference.so \
  --crosstool_top=//external:android/crosstool \
  --host_crosstool_top=@bazel_tools//tools/cpp:toolchain \
  + --cxxopt=-std=c++11 \
  --cpu=armeabi-v7a
  ```
  