Auto-update dependencies. [(#1133)](GoogleCloudPlatform/python-docs-samples#1133)

* Auto-update dependencies.

* Fix missing http library

Change-Id: I99faa600f2f3f1f50f57694fc9835d7f35bda250

Author: dpebot

samples/snippets/requirements.txt

@@ -1,2 +1,4 @@
-google-api-python-client==1.6.3
+google-api-python-client==1.6.4
+google-auth==1.1.1
+google-auth-httplib2==0.0.2
 google-cloud==0.27.0