Update to the new NUR format

See https://github.com/nix-community/NUR/issues/45

overlay.nix

@@ -4,12 +4,18 @@
 
 self: super:
 
-import ./default.nix {
-  callPackage = super.callPackage;
-  libsForQt5 = super.libsForQt5;
-  haskellPackages = super.haskellPackages;
-  pythonPackages = super.pythonPackages;
-  # ...
-  # Add here other callPackage/callApplication/... providers as the need arises
-}
+let filterSet =
+      (f: g: s: builtins.listToAttrs
+        (map
+          (n: { name = n; value = builtins.getAttr n s; })
+          (builtins.filter
+            (n: f n && g (builtins.getAttr n s))
+            (builtins.attrNames s)
+          )
+        )
+      );
+in filterSet
+     (n: !(n=="lib"||n=="overlays"||n=="modules")) # filter out non-packages
+     (p: true) # all packages are ok
+     (import ./default.nix { pkgs = super; })