Update Dockerfile

docker/Dockerfile

@@ -6,7 +6,6 @@ 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 \
@@ -22,7 +21,6 @@ RUN apt-get update && \
     libldap2-dev \
     npm git \
     python-virtualenv \
-    virtualenv && \
     apt-get clean  && \
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*