Bump version to 0.8.1

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
Merge branch 'master' of https://github.com/mcclurmc/ocaml-opasswd
First shot at replacing C stubs with Ctypes

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>