dotprofile.org: Setup nix with nixpkgs and staging

Just correspond with nixpkgs master and staging. More to likely come.

dotprofile.org

@@ -262,7 +262,7 @@ nix_env_setup()
   # BAD INSTALLER NO COOKIE!
   if [ -e ${HOME}/.nix-profile/etc/profile.d/nix.sh ]; then
       . ${HOME}/.nix-profile/etc/profile.d/nix.sh;
-      export NIX_PATH=${HOME}/src/github.com/NixOS/nixpkgs:nixpkgs=${HOME}/src/github.com/NixOS/nixpkgs
+      export NIX_PATH=nixpkgs=${HOME}/src/github.com/NixOS/nixpkgs:staging=${HOME}/src/github.com/NixOS/nixpkgs/staging
       export NIX_CFLAGS_COMPILE="-idirafter /usr/include"
       export NIX_CFLAGS_LINK="-L/usr/lib"
       export PKG_CONFIG_PATH="~/.nix-profile/lib/pkgconfig"