title: Multiple subscriptions to a topic
body: <p>I have been using pubsub for a bit of asynchronous work, and was wondering why someone may create multiple subscriptions for a single topic. My default values are as follows:</p>
  
  <pre><code>project_id = 'project'
  topic_name = 'app'
  subscription_name = 'general'
  </code></pre>
  
  <p>The routing of the actual function -- and how to process that -- is being doing in the <code>subscriber</code> receiver itself.</p>
  
  <p>What would be reasons why there would be various subscription names? The only thing I can think of is to spread items across multiple servers for processing, such as:</p>
  
  <pre><code>server1 -- `main-1`
  server2 -- `main-2`
  etc.
  </code></pre>
  
  <p>Are there any other reasons why a subscription name would not work well with one value?</p>