Improve khal notification

Ensure all dependencies are declared.
Also update calendar to reflect latest module changes

home/modules/programs/khal-notification.nix

@@ -7,14 +7,21 @@ let
 
   notificationScript = pkgs.writeShellApplication {
     name = "khal-notification";
+
+    runtimeInputs = [
+      pkgs.coreutils-full
+      pkgs.khal
+      pkgs.libnotify
+    ];
+
     text = ''
       date=$(date "+%H:%M:00")
-      events=$(${pkgs.khal}/bin/khal list --notstarted "$date" "$1")
+      events=$(khal list --notstarted "$date" "$1")
       if [ -z "$events" ]; then
         exit 0;
       fi
 
-      ${pkgs.libnotify}/bin/notify-send \
+      notify-send \
         --urgency=critical \
         --expire-time=90000 \
         --icon="${config.gtk.iconTheme.package}/share/icons/${config.gtk.iconTheme.name}/32/apps/office-calendar.svg" \