Update opam file

opam

@@ -1,10 +1,12 @@
-opam-version: "1.2"
+opam-version: "2.0"
+synopsis: "Protocol Buffers, JSON and XML serialization system for OCaml"
+authors: "Anton Lavrik <[email protected]>"
 maintainer: "Anton Lavrik <[email protected]>"
-author: "Anton Lavrik <[email protected]>"
 homepage: "https://github.com/alavrik/piqi-ocaml"
 bug-reports: "https://github.com/alavrik/piqi-ocaml/issues"
 build: [
   [make]
+  [make "test"] {with-test}
 ]
 install: [
   [make "DESTDIR=%{prefix}%" "install"]
@@ -13,11 +15,11 @@ remove: [
   ["rm" "-f" "%{prefix}%/bin/piqic-ocaml"]
   ["ocamlfind" "remove" "piqirun"]
 ]
-build-test: [make "test"]
-available: [ ocaml-version >= "4.02.0" ]
+flags: light-uninstall
 depends: [
-  "ocamlfind"
+  "ocaml" {>= "4.02.0"}
+  "ocamlfind" {build}
   "piqilib"
-  "num" {test}
+  "num" {with-test}
 ]
 dev-repo: "git://github.com/alavrik/piqi-ocaml"