There are many cram formatted files in the track hub registry (e.g., http://trackhubregistry.org/search/view_trackhub/AVrIY24vpL2YcDCmVC0g)
I don't know anything about the cram format, so I'm hoping you have plans to support this format.
PS. I did run into the XMLHttpRequest restriction on cross origin ftp access, so you would need to download the hub.txt and friends from ftp://ftp.ensemblgenomes.org/pub/misc_data/Track_Hubs/DRP000315/
There are many cram formatted files in the track hub registry (e.g., http://trackhubregistry.org/search/view_trackhub/AVrIY24vpL2YcDCmVC0g)
I don't know anything about the cram format, so I'm hoping you have plans to support this format.
PS. I did run into the XMLHttpRequest restriction on cross origin ftp access, so you would need to download the hub.txt and friends from ftp://ftp.ensemblgenomes.org/pub/misc_data/Track_Hubs/DRP000315/