Moving Specimen files out of repo

[oxinabox]

We have example files for each version and each format and each compression stored in tests/specimens

They are static files,
and really should not be in the repo.
They are a good candidate to move out to a DataDep.

They are not too large so there is no huge pressure to do it.
But over time we will gather more and more of them.
And eventually for #14
we are going to want some fairly large ones.

So we should move them @rofinn suggests we should make a public S3 bucket for them.