Add maven to Java stack

Author: Aaron O'Mullan

stacks/java/Dockerfile

@@ -16,6 +16,9 @@ cd /tmp ; dpkg -i /fuse.deb;
 # Install JDK
 RUN apt-get install -y --no-install-recommends openjdk-7-jdk
 
+# Install Maven
+RUN apt-get install -y maven
+
 # Default init command
 CMD su codebox /opt/codebox/init.sh