Remove maintainership

With this patch I remove myself as a maintainer for all packages I
currently maintain.

This is due the fact that I will be basically off the grid from May 2018
until early 2019, as I will be on a trip through north america.

I will revert this patch as soon as I'm back, as I plan to continue
contributing to nixpkgs then.
But as I cannot maintain anything during that time, I'd like to get this
patch merged.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

pkgs/applications/misc/khal/default.nix

@@ -40,6 +40,6 @@ buildPythonApplication rec {
     homepage = http://lostpackets.de/khal/;
     description = "CLI calendar application";
     license = licenses.mit;
-    maintainers = with maintainers; [ matthiasbeyer jgeerds ];
+    maintainers = with maintainers; [ jgeerds ];
   };
 }