Support parquet format for tensorflow-io

[yongtang]

There are quite some interests to support parquet for tensorflow and a PR (tensorflow/tensorflow#19461) has already been approved.

With the expected deprecation of tf.contrib, it makes sense to move PR tensorflow/tensorflow#19461 to tensorflow-io.

At the moment the blocking issue with the related PR is the bazel version. The PR requires bazel 1.7.1+ to incorporate boost library while tensorflow CI still uses bazel 1.5.0. We will need to find out a way to work out the bazel version issue. See tensorflow/tensorflow#22449, tensorflow/tensorflow#22964 for details.