ZOOKEEPER-2998: CMake declares incorrect ZooKeeper version

This was not updated for the current development branch; it should be
3.6.0.

Author: Andrew Schwartzmeyer <andrew@schwartzmeyer.com>

Reviewers: Michael Han <hanm@apache.org>

Closes #484 from andschwa/ZOOKEEPER-2998

src/c/CMakeLists.txt

@@ -16,7 +16,7 @@
 
 cmake_minimum_required(VERSION 3.6)
 
-project(zookeeper VERSION 3.5.3)
+project(zookeeper VERSION 3.6.0)
 set(email user@zookeeper.apache.org)
 set(description "zookeeper C client")