Added statsd integration into the API

- new client for statsd, follows conventions used elsewhere for configuration
- client wraps underlying library so we can use a config property to send/not send statsd

Added statsd metrics for:
- count of API successful calls SMS/Email
- count of successful task execution for SMS/Email
- count of errors from Client libraries
- timing of API calls to third party clients
- timing of how long messages live on the SQS queue

app/notifications/process_client_response.py

@@ -1,5 +1,7 @@
 import uuid
 from flask import current_app
+
+from app import statsd_client
 from app.dao import notifications_dao
 from app.clients.sms.firetext import get_firetext_responses
 from app.clients.sms.mmg import get_mmg_responses
@@ -67,5 +69,6 @@ def process_sms_client_response(status, reference, client_name):
                                                                                     reference,
                                                                                     notification_status_message))
 
+    statsd_client.incr('notifications.callback.{}.{}'.format(client_name.lower(), notification_statistics_status))
     success = "{} callback succeeded. reference {} updated".format(client_name, reference)
     return success, errors