Merge pull request #9 from herd/4.02-warns

Avoid some OCaml 4.02 warnings
Adapt for ocaml 4.02.0
Notice the conditional build system, which sould be transparent to users....
Version increment
Add lib/bytes.ml{,i} to the .gitignore
Use the safe_string ocamlbuild tag instead of giving it as parameter and simplify the scripting using a single shell script