docker best practices

[0xaf1f]

http://singularity.lbl.gov/docs-docker#best-practices lists some guidelines for building docker images that will convert nicely into singularity images. There is also some information over at https://github.com/singularityware/docker2singularity#tips-for-making-docker-images-compatible-with-singularity. Maybe it'd be a good idea for the additional points from there to be added to the documentation in the docs-docker page.