Add DNS support for PWD instances (#94)

* Add DNS support for PWD instances

* Store IP address of PWD in all session networks and restore it with the
same IP address

* Remove unnecesary print

* Change url format to pwd<ip>-port for better DNS filtering

* Make PWD listen on 80 and 443 for DNS resolve to work

docker-compose.yml

@@ -9,8 +9,8 @@ services:
         command: /bin/sh -c 'cd /go/src/github.com/franela/play-with-docker; go run api.go'
         ports:
             # app exposes port 3000
-            - "3000:3000"
-            - "3001:3001"
+            - "80:3000"
+            - "443:3001"
         volumes:
             # since this app creates networks and launches containers, we need to talk to docker daemon
             - /var/run/docker.sock:/var/run/docker.sock