Add routing and pages for managing templates

So that users can see what it the flow is like to:
- add new templates
- edit existing templates

tests/app/main/views/test_templates.py

@@ -0,0 +1,17 @@
+def test_should_return_list_of_all_templates(notifications_admin):
+    response = notifications_admin.test_client().get('/templates')
+
+    assert response.status_code == 200
+
+
+def test_should_show_page_for_one_templates(notifications_admin):
+    response = notifications_admin.test_client().get('/templates/template')
+
+    assert response.status_code == 200
+
+
+def test_should_redirect_when_saving_a_template(notifications_admin):
+    response = notifications_admin.test_client().post('/templates/template')
+
+    assert response.status_code == 302
+    assert response.location == 'http://localhost/templates'