Update Dockerfile

docker/Dockerfile

@@ -6,6 +6,7 @@ FROM debian:jessie
 MAINTAINER Theodotos Andreou theodotos.andreou@puri.sm
 
 RUN apt-get update && \
+    apt-get -q -y dist-upgrade && \
     apt-get install -q -y \
     software-properties-common \
     python-software-properties \