Order difference in order of disturbance

Author: rhpvorderman

README.rst

@@ -130,7 +130,10 @@ Differences with zlib and gzip modules
 + Compression level 0 in ``zlib`` and ``gzip`` means **no compression**, while
   in ``isal_zlib`` and ``igzip`` this is the **lowest compression level**.
   This is a design choice that was inherited from the ISA-L library.
-+ Compression levels range from 0 to 3, not 1 to 9.
++ Compression levels range from 0 to 3, not 1 to 9. ``isal_zlib.Z_DEFAULT_COMPRESSION``
+  has been aliased to ``isal_zlib.ISAL_DEFAULT_COMPRESSION`` (2).
++ ``isal_zlib`` only supports ``NO_FLUSH``, ``SYNC_FLUSH``, ``FULL_FLUSH`` and
+  ``FINISH_FLUSH``. Other flush modes are not supported and will raise errors.
 + ``zlib.Z_DEFAULT_STRATEGY``, ``zlib.Z_RLE`` etc. are exposed as
   ``isal_zlib.Z_DEFAULT_STRATEGY``, ``isal_zlib.Z_RLE`` etc. for compatibility
   reasons. However, ``isal_zlib`` only supports a default strategy and will
@@ -139,11 +142,14 @@ Differences with zlib and gzip modules
   ``isal_zlib`` supports memory levels smallest, small, medium, large and
   largest. These have been mapped to levels 1, 2-3, 4-6, 7-8 and 9. So
   ``isal_zlib`` can be used with zlib compatible memory levels.
-+ ``isal_zlib`` only supports ``NO_FLUSH``, ``SYNC_FLUSH``, ``FULL_FLUSH`` and
-  ``FINISH_FLUSH``. Other flush modes are not supported and will raise errors.
++ ``isal_zlib`` methods have a ``data`` argument which is positional only. In
+  isal_zlib this is not enforced and it can also called as keyword argument.
+  This is due to implementing ``isal_zlib`` in cython and maintaining backwards
+  compatibility with python 3.6.
 + ``igzip.open`` returns a class ``IGzipFile`` instead of ``GzipFile``. Since
   the compression levels are not compatible, a difference in naming was chosen
-  to reflect this. ``igzip.GzipFile`` does exist as an alias however.
+  to reflect this. ``igzip.GzipFile`` does exist as an alias of
+  ``igzip.IGzipFile`` for compatibility reasons.
 
 Contributing
 ------------