message: README.md update to include R installation and testing
  This fix updates README.md to include R installation steps
  and testing run.
diff: @@ -44,6 +44,8 @@ be able to find the correct path to the module.
  ## Developing
  +### Python
  +
  The TensorFlow I/O package (`tensorflow-io`) could be built from source:
  ```sh
  $ docker run -it -v ${PWD}:/working_dir -w /working_dir tensorflow/tensorflow:custom-op
  @@ -55,6 +57,27 @@ $ bazel-bin/build_pip_pkg artifacts
  A package file `artifacts/tensorflow_io-*.whl` will be generated after a build is successful.
  +### R
  +
  +The docker image `tensorflow/tensorflow:custom-op` does not have R installation.
  +Instead, the latest R package is available from
  +[CRAN](https://cran.r-project.org/bin/linux/ubuntu/README.html).
  +
  +After the successful installation of `R`(`r-base`) from CRAN, the following installation steps
  +are also needed:
  +```
  +$ # In docker
  +$ apt-get -y -qq update
  +$ apt-get -y -qq install build-essential libcurl4-gnutls-dev libxml2-dev libssl-dev
  +$ R -e 'install.packages(c("devtools", "testthat", "tensorflow", "tfdatasets"), dependencies = TRUE)'
  +```
  +
  +With all prerequisites packages installed, it is possible to run test with:
  +```
  +$ # In docker
  +$ R -e "devtools::test()"
  +```
  +
  ## License
  [Apache License 2.0](LICENSE)
  