Fix Dockerfile for new repo layout

Dockerfile

@@ -4,7 +4,9 @@ EXPOSE     9090
 VOLUME     [ "/prometheus" ]
 WORKDIR    /prometheus
 
-ENTRYPOINT [ "/prometheus-src/.build/package/run_prometheus.sh" ]
+ENTRYPOINT [ "/prometheus-src/prometheus", "-config.file=/prometheus.conf" ]
 RUN        apt-get update && apt-get install -yq make git curl sudo mercurial vim-common
 ADD        . /prometheus-src
 RUN        cd /prometheus-src && make tools binary
+ADD        ./documentation/examples/prometheus.conf /prometheus.conf
+