Add section about permessage compression to README

Author: albertas

README.rst

@@ -105,6 +105,20 @@ should start with a slash, but not end with one; for example::
     daphne --root-path=/forum django_project.asgi:application
 
 
+Permessage compression
+----------------------
+
+Daphne supports and by default accepts  `permessage-deflate` compression
+(`permessage-deflate specification <http://tools.ietf.org/html/draft-ietf-hybi-permessage-compression>`_).
+Additional compressions `permessage-bzip2`, `permessage-snappy` might be enabled by installing
+`bz2` and `snappy` python packages in daphne environment. These compressions will also be accepted
+by default if needed packages were available. The compression implementation is provided by
+`Autobahn|Python <https://github.com/crossbario/autobahn-python>`_ package:
+`permessage-deflate <https://github.com/crossbario/autobahn-python/blob/master/autobahn/websocket/compress_deflate.py`_,
+`permessage-bzip2 <https://github.com/crossbario/autobahn-python/blob/master/autobahn/websocket/compress_bzip2.py`_,
+`permessage-snappy <https://github.com/crossbario/autobahn-python/blob/master/autobahn/websocket/compress_snappy.py`_.
+
+
 Python Support
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