Update docker-compose file to version 2

And snappass container will be built from Dockerfile since there is no official image (yet..)

docker-compose.yml

@@ -1,13 +1,17 @@
----
+version: '2'
-snappass:
+
-    image: snappass
+services:
+
+    snappass:
+        build: .
+        image: pinterest/snappass
         ports:
             - "5000:5000"
-    links:
-        - "redis:redis"
         environment:
             - REDIS_HOST=redis
             - NO_SSL=True
+        depends_on:
+          - redis
 
-redis:
+    redis:
         image: "redis:latest"