https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki
$ go get github.com/btcsuite/btcd/btcec
$ go get -u github.com/tnakagawa/bipschnorr
$ go test -count 1 -v github.com/tnakagawa/bipschnorr
$ go get github.com/btcsuite/btcd/btcec
$ go get -u github.com/tnakagawa/bipschnorr
$ go test -count 1 -v github.com/tnakagawa/bipschnorr -run ^TestMultisignature$
$ go test -count 1 -v github.com/tnakagawa/bipschnorr -run ^TestThreshold$