* libsodium: add latest versions, fix old versions
older versions of libsodium were added to an "old" subdirectory
* zeromq: add 4.1.4
prerequiste for the latest develop version of flux
Package repositories now look like this:
top-level-dir/
repo.yaml
packages/
libelf/
package.py
mpich/
package.py
...
This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).
