Automatically populate species/release/reference mapping

[tavinathanson]

See #114

@tavinathanson:

Being in the business of keeping all species up to date seems undesirable. We can't just use http://useast.ensembl.org/info/website/archives/assembly.html?redirect=no or something? I think you were asking around about a data source for this?

@iskandr:

I'm not happy about this either but it's the only easy way to get mice working for now. I wanted to get the species representation wired together first, maybe we can do a later PR to auto-populate from remote data?

This is the issue for that PR.