Updating Dockerfile to use current install script at https://get.docker/com/

Author: rheinwein

Dockerfile

@@ -10,7 +10,7 @@ RUN apt-get update -qq && apt-get install -qqy \
     iptables
 
 # Install Docker from Docker Inc. repositories.
-RUN curl -sSL https://get.docker.com/ubuntu/ | sh
+RUN curl -sSL https://get.docker.com/ | sh
 
 # Install the magic wrapper.
 ADD ./wrapdocker /usr/local/bin/wrapdocker