Add two-way messaging view

> Once an inbound message has been received, there should be a way to
> see the other messages in the system from the same service to the same
> number. Both in and outbound. Nice inbox/whatsapp stylee view or some
> such. This way the context of the reply is understood.
>
> Initially will only see the outbound template, not the actual message,
> but we’re going to change this for the rest (soon), so that you can
> always see the full message for all outbound.

app/notify_client/notification_api_client.py

@@ -54,3 +54,8 @@ class NotificationApiClient(NotifyAdminAPIClient):
                 url='/service/{}/notifications'.format(service_id),
                 params=params
             )
+
+    def get_notification(self, service_id, notification_id):
+        return self.get(
+            url='/service/{}/notifications/{}'.format(service_id, notification_id)
+        )

app/notify_client/service_api_client.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 from flask import url_for
 from app.utils import BrowsableItem
 from app.notify_client import _attach_current_user, NotifyAdminAPIClient
+from . import notification_api_client
 
 
 class ServiceAPIClient(NotifyAdminAPIClient):
@@ -244,11 +245,22 @@ class ServiceAPIClient(NotifyAdminAPIClient):
             params=dict(year=year)
         )
 
-    def get_inbound_sms(self, service_id):
+    def get_inbound_sms(self, service_id, user_number=''):
         return self.get(
-            '/service/{}/inbound-sms'.format(service_id)
+            '/service/{}/inbound-sms?user_number={}'.format(
+                service_id,
+                user_number,
+            )
         )['data']
 
+    def get_inbound_sms_by_id(self, service_id, notification_id):
+        return self.get(
+            '/service/{}/inbound-sms/{}'.format(
+                service_id,
+                notification_id,
+            )
+        )
+
     def get_inbound_sms_summary(self, service_id):
         return self.get(
             '/service/{}/inbound-sms/summary'.format(service_id)