start experimenting with opam

opam

+opam-version: "1.2"
+name: "iris"
+version: "dev"
+maintainer: "Ralf Jung <jung@mpi-sws.org>"
+authors: "The Iris Team"
+homepage: "http://iris-project.org/"
+bug-reports: "https://gitlab.mpi-sws.org/FP/iris-coq/issues"
+license: "BSD"
+dev-repo: "https://gitlab.mpi-sws.org/FP/iris-coq"
+build: [
+  [make]
+]
+install: [make "install"]
+remove: [ "sh" "-c" "rm -rf '%{lib}%/coq/user-contrib/iris'" ]
+depends: [
+  "coq" { ((>= "8.5.1" & < "8.7~") | (= "dev"))}
+  "coq-mathcomp-ssreflect" { ((>= "1.6" & < "1.7~") | (= "dev"))}
+]