Release version 4.0.0 (#34)

diff --git a/setup.py b/setup.py
index 4346622..c1ac11e 100755
--- a/setup.py
+++ b/setup.py
@@ -68,7 +68,7 @@
     python_requires='>=2.7',
     install_requires=['six'],
     url='https://github.com/GoogleChromeLabs/pywebsocket3',
-    version='3.0.2',
+    version='4.0.0',
 )
 
 # vi:sts=4 sw=4 et