META file does not contain the version string

with the released version 2.0.0: when I compile with "make", the META file does not contain a version string.
````
$ cat _build/install/default/lib/ocamlgraph/META 
description = ""
requires = "stdlib-shims"
archive(byte) = "graph.cma"
archive(native) = "graph.cmxa"
plugin(byte) = "graph.cma"
plugin(native) = "graph.cmxs"$
````