Use best pratice for apt-get

https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#run

debian/Dockerfile-stretch

@@ -2,15 +2,14 @@ FROM debian:stretch
 
 MAINTAINER antoinebarbare@gmail.com
 
-RUN apt-get update -y
-RUN apt-get install -y \
-	curl \
-	git \
-	gpg \
-	locate \
-	nano \
-	vim \
-	wget
+RUN apt-get update && apt-get install -y \
+    curl \
+    git \
+    gpg \
+    locate \
+    nano \
+    vim \
+    wget
 
 ENV TERM xterm
 CMD ["/bin/bash"]