v1.0.0

CHANGES:

• explicit sexplib dependency, compatible with cstruct 4.0.0 (#99, @TheLortex)
• charrua-server is an independent opam package now (#100, @hannesm)
• charrua is the new name for charrua-core (#100, @hannesm)
• the repository moved to https://github.com/mirage/charrua