pythonPackages.cerberus: Move to own file

pkgs/development/python-modules/cerberus/default.nix

@@ -0,0 +1,17 @@
+{ stdenv, buildPythonPackage, fetchPypi }:
+
+buildPythonPackage rec {
+  pname = "Cerberus";
+  version = "0.9.2";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "1km7hvns1snrmcwz58bssi4wv3gwd34zm1z1hwjylmpqrfrcf8mi";
+  };
+
+  meta = with stdenv.lib; {
+    homepage = http://python-cerberus.org/;
+    description = "Lightweight, extensible schema and data validation tool for Python dictionaries";
+    license = licenses.mit;
+  };
+}