README: git clone with https
README: git clone with https

Clone via https:// rather than git:// since it's more widely accessible.

[1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org: augment commit message]
Reviewed-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>
Tested-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

ToxicFrog/bup,ToxicFrog/bup,ToxicFrog/bup,ToxicFrog/bup,ToxicFrog/bup