updating README to give instruction for building with Singularity 2.4
updating README to give instruction for building with Singularity 2.4
containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps,containers-ftw/apps