message: Mention tensorflow-io-nightly package in README
diff: @@ -28,6 +28,12 @@ The `tensorflow-io` Python package could be installed with pip directly:
  $ pip install tensorflow-io
  ```
  +People who are a little more adventurous can also try our nightly binaries:
  +```
  +$ pip install tensorflow-io-nightly
  +```
  +
  +
  The related module such as Kafka could be imported with python:
  ```
  $ python
  