Add a warning to the stream module docs
This wwarning highlights that the stream module is considered experimental
and unmaintained.
lz4.stream sub-package
======================
+.. warning::
+ This module is unmaintained.
+
+ This sub-package is considered experimental. It was submitted by a community
+ member who is not able to continue to maintain the module.
+
+ This module is not built as part of the distributed wheels. If you wish to
+ build and use this module you will need to download and build from source
+ with the environment variable PYLZ4_EXPERIMENTAL set to TRUE.
+
+ The module needs some re-write, and the tests need extensive work, for this
+ to become production ready. If you are interested in working on this, please
+ reach out to the package maintainers.
+
This sub-package provides the capability to compress and decompress data using
the `stream specification
<https://github.com/lz4/lz4/blob/master/examples/streaming_api_basics.md>`_,
