Auto-update dependencies. [(#1980)](GoogleCloudPlatform/python-docs-samples#1980)

* Auto-update dependencies.

* Update requirements.txt

* Update requirements.txt

Author: dpebot

samples/snippets/requirements.txt

@@ -1,5 +1,5 @@
-google-api-python-client==1.7.4
-google-auth==1.6.1
+google-api-python-client==1.7.8
+google-auth==1.6.2
 google-auth-httplib2==0.0.3
 google-cloud==0.34.0
-google-cloud-storage==1.13.0
+google-cloud-storage==1.13.2