v0.1.0-rc: remove core and packet dependencies

The library no longer depends on them after the rewrite.
v0.1.0-rc: stop using opam-street

No longer necessary, as core is no longer a dependency.
v0.1.0-rc: remove ocaml version, test more versions
v0.1.0-rc: update README, add LICENSE file
v0.1.0-rc: set version number to 0.1.0