Release google-auth-library-python 1.6.0 (#303)

diff --git a/setup.py b/setup.py
index 1d603c7..f86748c 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@
 
 setup(
     name='google-auth',
-    version='1.5.1',
+    version='1.6.0',
     author='Google Cloud Platform',
     author_email='jonwayne+google-auth@google.com',
     description='Google Authentication Library',