Add missing functionality from old repo

@stevengj I deleted the old repo to avoid confusion for users, this is all the old functionality ported to this repo
Wouldn't it be better to return a `type CompressorInfo` here than a `Dict`, since the fields are always the same?

(In practice, I'm not sure it's worthwhile to try to output all this info, because the auto-installed Blosc binaries will only have the `blosclz` compressor anyway.  That's why I just returned a list of strings before.)