contrib/docker/centos7

--- a/contrib/docker/centos7	Thu Aug 24 18:40:30 2017 +0200
+++ b/contrib/docker/centos7	Sun Oct 01 01:02:22 2017 +0200
@@ -1,9 +1,12 @@
 FROM centos:centos7
-RUN yum install -y gcc
-RUN yum install -y python-devel python-docutils
-RUN yum install -y make
-RUN yum install -y rpm-build
-RUN yum install -y gettext
-RUN yum install -y tar
+RUN yum install -y \
+	gcc \
+	gettext \
+	make \
+	python-devel \
+	python-docutils \
+	rpm-build \
+	tar
+
 # For creating repo meta data
 RUN yum install -y createrepo