Write release notes for 2.0.0 release and added upgrade instructions for the release

Author: Grokzen

docs/release-notes.rst

@@ -1,6 +1,25 @@
 Release Notes
 =============
 
+2.0.0 (Aug 12, 2019)
+
+Specific changes to redis-py-cluster is mentioned below here. 
+
+    * Update entire code base to now support all redis-py version in the 3.0.x version line. Any future redis-py version will be supported at a later time.
+    * Major update to all tests to mirror the code of the same tests from redis-py
+    * Dropped support for the 2.10.6 redis-py release.
+    * Add pythoncodestyle lint validation check to travis-ci runs to check for proper linting before accepting PR:s
+    * Class StrictRedisCluster was renamed to RedisCluster
+    * Class StrictRedis has been removed to mirror upstream class structure
+    * Class StrictClusterPipeline was renamed to ClusterPipeline
+    * Fixed travis-ci tests not running properly on python 3.7
+    * Fixed documentation regarding threads in pipelines
+    * Update lit of command callbacks and parsers. Added in "CLIENT ID"
+    * Removed custom implementation of SORT and revert back to use same-slot mechanism for that command.
+    * Added better exception message to get_master_node_by_slot command to help the user understand the error.
+    * Improved the exception object message parsing when running on python3
+
+
 1.3.6 (Nov 16, 2018)
 --------------------
 

docs/upgrading.rst

@@ -3,6 +3,20 @@ Upgrading redis-py-cluster
 
 This document describes what must be done when upgrading between different versions to ensure that code still works.
 
+1.3.x --> 2.0.0
+---------------
+
+Redis-py upstream package dependency has now been updated to be any of the releases in the major version line 3.0.x. This means that you must upgrade your dependency from 2.10.6 to the latest version. Several internal components have been updated to reflect the code from 3.0.x.
+
+Class StrictRedisCluster was renamed to RedisCluster. All usages of this class must be updated.
+
+Class StrictRedis has been removed to mirror upstream class structure.
+
+Class StrictClusterPipeline was renamed to ClusterPipeline.
+
+Method SORT has been changed back to only allow to be executed if keys is in the same slot. No more client side parsing and handling of the keys and values.
+
+
 1.3.2 --> Next Release
 ----------------------