add redis no docker compose e no travis

.travis.yml

@@ -5,6 +5,7 @@ python:
 
 services:
   - postgresql
+  - redis-server
 
 install:
   - pip install -r requirements/test-requirements.txt

docker-compose.yml

@@ -10,6 +10,11 @@ sapldb:
     - sapldb_data:/var/lib/postgresql/data/
   ports:
     - "5432:5432"
+saplredis:
+  image: redis:5.0.3-stretch
+  restart: always
+  ports: 
+    - "6379:6379"
 sapl:
   image: interlegis/sapl:3.1.146
   restart: always
@@ -29,5 +34,6 @@ sapl:
     - sapl_media:/var/interlegis/sapl/media
   links:
     - sapldb
+    - saplredis
   ports:
     - "80:80"