Concerning the use of Skein

[DonaldTsang]

https://github.com/multiformats/go-multihash is going to use Hashland's skein hash (see https://github.com/multiformats/multicodec/blob/master/table.csv#L131)
Reference: multiformats/go-multihash#52 and https://godoc.org/leb.io/hashland/skein

[tildeleb]

Thank for submitting this issue. Skein was included by accident and I have removed it.