Add RecordInput documentation to tf.contrib.framework

This fix tries to address the issue raised in 10622
where the RecordInput is not available in the documentation.
As was suggested in 10622, this fix exposes RecordInput
to tf.contrib (tf.contrib.framework) so that
docs could shown up.

This fix fixes 10622.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>