Add singularity builder container

base/singularity:2.5

+FROM debian:stretch
+
+  RUN apt-get update -qq && apt-get install -y wget bzip2 python-pip git
+  RUN apt-get install -y build-essential squashfs-tools libtool autotools-dev libarchive-dev automake autoconf uuid-dev libssl-dev
+
+  RUN pip install sregistry[all]
+  RUN sed -i -e 's/^Defaults\tsecure_path.*$//' /etc/sudoers
+  RUN cd /tmp && git clone -b vault/release-2.5 https://www.github.com/sylabs/singularity.git && cd singularity && /autogen.sh && ./configure --prefix=/usr/local && make && make install