Define polymorphic lenses and compile the runtime library

fieldglass.opam

@@ -0,0 +1,11 @@
+opam-version: "1.2"
+name: "fieldglass"
+version: "0.1.0"
+maintainer: "rack"
+authors: ["rack"]
+homepage: "https://github.com/rackquiem/fieldglass"
+bug-reports: "https://github.com/rackquiem/fieldglass/issues"
+dev-repo: "git+https://github.com/rackquiem/fieldglass.git"
+build: [make]
+build-test: [make "test"]
+available: [ocaml-version = "4.06.1"]