Added 'Custom' class.

Quadrature.py

@@ -39,3 +39,12 @@ class Gauss(Quadrature):
 
     def get_name(self):
         return self.__class__.__name__ + str(self._num_eval_points)
+
+
+class Custom(Quadrature):
+    def _reset(self, config):
+        super()._reset(config)
+
+        self._eval_points = config.pop('eval_points', [0])
+        self._num_eval_points = len(self._eval_points)
+        self._weights = [1] * self._num_eval_points