sns for catracker

gistfile1.txt

Add a `.env` variable, `NOTIFICATION_EMAIL`

Then update the `run_stack_command` fabric task to pass that to cloudformattion as `NotificationEmail`.

# then in template.yml

Parameters:
  ...
  NotificationEmail:
    Type: String

Resources:
  ...
  CATrackerNotificationTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: !Sub "${AWS::StackName}-notification-topic"
      Subscription:
        - Protocol: email
          Endpoint: !Ref NotificationEmail
 
Outputs:
  ...
  SNSTopicArn:
    Description: CATracker SNS Arn
    Value: !Ref CATrackerNotificationTopic
    
OK, now that the SNS topic is in the stack outputs you'll be able to get it via the `stack_exports` return value 
in the fabric tasks and add it to the remote app's `.env` in the same way the "RDSEndpoint" and "ELBEndpoint" get
used in the `app_configure` task.

The check out the `publish` method in the SNS boto3 docs
http://boto3.readthedocs.io/en/latest/reference/services/sns.html#client