update OPAM script

Author: mgree

libdash.opam

@@ -31,6 +31,10 @@ build: [
   ["./ldconfig.sh"] # fix up .so files if ldconfig didn't do it
   [make "-C" "ocaml" "test"] {with-test}
 ]
+install: [
+  ["opam-installer" "--prefix=%{prefix}%" "libdash.install"]
+  [make "-C" "test" "test"] {with-test}
+]
 dev-repo: "git+https:///github.com/mgree/libdash"
 url {
   src: "https://github.com/mgree/libdash/archive/v0.1.tar.gz"