More helpful error message when compressor is missing

[eslavich]

Currently we indicate which compression label can't be found:

https://github.com/asdf-format/asdf/blob/ba09e57d9344206016127d1a86d3319a2df9f2ec/asdf/compression.py#L50

but since the metadata in the tree includes the python package and version, we could do better and suggest a package to install.