make copy paste user friendly

copying only the first line killed my sources.list file

docs/sources/installation/ubuntulinux.rst

@@ -78,7 +78,8 @@ Docker is available as a Debian package, which makes installation easy.
    sudo sh -c "wget -qO- https://get.docker.io/gpg | apt-key add -"
 
    # Add the Docker repository to your apt sources list.
-   sudo sh -c "echo deb http://get.docker.io/ubuntu docker main > /etc/apt/sources.list.d/docker.list"
+   sudo sh -c "echo deb http://get.docker.io/ubuntu docker main\
+   > /etc/apt/sources.list.d/docker.list"
 
    # Update your sources
    sudo apt-get update