Update changelog

Author: Jon Wayne Parrott

CHANGELOG

@@ -1,3 +1,16 @@
+v1.5.1
+  Version 1.5.1
+
+  Bugfix release
+
+  - Allow using versions of oauth2client < 2.0.0. (#197)
+  - Check both current and new API discovery URL. (#202)
+  - Retry http requests on connection errors and timeouts. (#218)
+  - Retry http requests on rate limit responses. (#201)
+  - Import guards for ssl (for Google App Engine). (#220)
+  - Use named loggers instead of the root logger. (#206)
+  - New search console example. (#212)
+
 v1.5.0
   Version 1.5.0