riemann-dash: Wrap to keep bundler and sass out of user env

pkgs/servers/monitoring/riemann-dash/default.nix

@@ -1,8 +1,26 @@
-{ bundlerEnv }:
+{ bundlerEnv, lib, stdenv }:
 
-bundlerEnv {
+let
-  name = "riemann-dash-0.2.9";
+  name = "riemann-dash-${env.gems.riemann-dash.version}";
-  gemfile = ./Gemfile;
+
-  lockfile = ./Gemfile.lock;
+  env = bundlerEnv {
-  gemset = ./gemset.nix;
+    inherit name;
+    gemfile = ./Gemfile;
+    lockfile = ./Gemfile.lock;
+    gemset = ./gemset.nix;
+  };
+
+in stdenv.mkDerivation {
+  inherit name;
+  buildCommand = ''
+    mkdir -p $out/bin
+    ln -s ${env}/bin/riemann-dash $out/bin/riemann-dash
+  '';
+
+  meta = with lib; {
+    description = "A javascript, websockets-powered dashboard for Riemann";
+    homepage = https://github.com/riemann/riemann-dash;
+    license = licenses.mit;
+    platforms = platforms.unix;
+  };
 }