Register JLDArchives: v0.0.1

A new package for archiving examples of JLD files. Over time, these become useful for making sure we haven't broken backwards-compatibility. I didn't want to add large-ish .jld files to the HDF5/JLD package, so this is the solution I came up with.

My plan would be to add this as a test on Travis for HDF5's tests, so these backwards-compatibility tests will be run frequently.

I won't hit "merge" myself right away, to give people a chance to bikeshed the name and strategy.