Small project updates

- bumped dune and opam versions
- Added synopsis in opam file
- small doc adjustments

dune-project

@@ -1,3 +1,2 @@
-(lang dune 1.0)
+(lang dune 1.8)
 (name libusb)
-(version 2018-07-12-1)

lib/libusb.mli

@@ -6,12 +6,11 @@
 
     I wrote this alternate binding:
     - in order to experiment more in depth with {{:https://github.com/ocamllabs/ocaml-ctypes} Ctypes};
-    - and because I needed something more portable than {{:https://github.com/letoh/ocaml-usb} ocaml-usb}: this one is working on Windows. *)
+    - and because I needed something more portable than {{:https://github.com/letoh/ocaml-usb} ocaml-usb}: this one is working on Windows, which was not the case of ocaml-usb when I started this project. *)
 
 include module type of T
 
-
+(** {1 Getting more of errors} *)
-(** {1 Getting more of {! error}s} *)
 
 val string_of_error: error -> string
 
@@ -44,7 +43,7 @@ val init_libusb: unit -> (unit, error) result
 (** This function must be called before calling any other libusb function. *)
 
 val exit_libusb: unit -> unit
-(** Should be called after closing all open devices and before your application
+(** Should be called after closing all opened devices and before your application
    terminates. *)
 
 val get_version: unit -> version

libusb.opam

@@ -1,15 +1,11 @@
-opam-version: "1.2"
+opam-version: "2.0"
-version: "2018-07-12-1"
+version: "2019-03-21-1"
 maintainer: "Matthieu Dubuget <matthieu.dubuget@gmail.com>"
 authors: "Matthieu Dubuget <matthieu.dubuget@gmail.com>"
-
+synopsis: "Binding to a tiny part of http://libusb.info libusb"
 homepage: "none"
 bug-reports: "Matthieu Dubuget <matthieu.dubuget@gmail.com>"
-
+build: [ [ "dune" "build" "-p" name "-j" jobs ]]
-build: [
-  [ "dune" "build" "-p" name "-j" jobs ]
-]
-
 license: "Not yet decided"
 depends: [
   "dune" {build}