Add protobuf dep and install instructions (#2250)

Author: averikitsch

tasks/README.md

@@ -23,6 +23,18 @@ Please refer to [Setting Up a Python Development Environment](https://cloud.goog
 To set up authentication, please refer to our
 [authentication getting started guide](https://cloud.google.com/docs/authentication/getting-started).
 
+## Install Dependencies
+
+To install the dependencies for this sample, use the following command:
+
+```
+pip install -r requirements.txt
+```
+
+This sample uses the common protos in the [googleapis](https://github.com/googleapis/googleapis)
+repository. For more info, see
+[Protocol Buffer Basics](https://developers.google.com/protocol-buffers/docs/pythontutorial).
+
 ## Creating a queue
 
 To create a queue (named `my-queue`) using the Cloud SDK, use the following

tasks/requirements.txt

@@ -1,3 +1,4 @@
 Flask==1.0.2
 gunicorn==19.9.0
-google-cloud-tasks==0.7.0
+google-cloud-tasks==1.1.0
+googleapis-common-protos==1.6.0