Fix lexicographic ordering when timestamps are the same

[TheInnerLight]

ULIDs are currently not lexicographically sortable unless they have the same timestamp.

This is also has alarming consequences where members Sets of ULID will be treated as equal if the timestamps are the same but have different random components.

This change ensures that they will be sorted correctly even if the timestamps are identical.

See also: https://github.com/haskell-github-trust/ulid/issues/15