optimize byte swap in base62 encoding (#50)

Co-authored-by: Tom Hacohen <tasn@users.noreply.github.com>

add go.mod

uint128 ops are much faster without loops. (#36)

Fix issue 25 (#26)

* fix panic on parsing invalid KSUID representations

* more tests

* cleanup

Fix issue 25 (#26)

* fix panic on parsing invalid KSUID representations

* more tests

* cleanup

Fix CompressedSetIter when set ends in a sequence (#24)

Fix CompressedSetIter when set ends in a sequence (#24)