fix(router): docker build fails when apt archive is stale

`apt-get update` before the first apt command seems to fix this
in general.

Author: mboersma

router/Dockerfile

@@ -2,7 +2,8 @@ FROM deis/base
 MAINTAINER Gabriel Monroy <gabriel@opdemand.com>
 
 # install nginx
-RUN apt-get install -yq python-software-properties
+RUN apt-get update && \
+    apt-get install -yq python-software-properties
 RUN add-apt-repository ppa:chris-lea/redis-server -y
 RUN add-apt-repository ppa:nginx/stable -y
 RUN apt-get update