Speed up building, a lot

Dockerfile

 FROM debian:jessie
+RUN apt-get update && apt-get -y upgrade
+RUN apt-get install -y curl build-essential debhelper dh-autoreconf dh-systemd autotools-dev libssl-dev nettle-dev docbook2x
 WORKDIR /root/
 COPY patches patches
 COPY build.sh build.sh
-RUN apt-get update && apt-get -y upgrade
-RUN apt-get install -y curl build-essential debhelper dh-autoreconf dh-systemd autotools-dev libssl-dev nettle-dev docbook2x
 RUN ./build.sh
 CMD tar c *.deb

README.md

@@ -7,6 +7,6 @@ This docker will generate a .deb package for Radsecproxy.
 Edit **build.sh** and set the desired version number for Radsecproxy.
 
 ```
-docker build --no-cache -t radsecproxy-debbuild .
+docker build -t radsecproxy-debbuild .
 docker run -i radsecproxy-debbuild | tar x
 ```