code: function del(obj, key, immutable) {
      if (immutable)
          return _del(assign({}, obj), key);
      return _del(obj, key);
  }
docs: Del
  Removes a property within the supplied object.
  
  @param obj the object to inspect.
  @param key the dot notated key or array of keys.
  @param immutable when true original object NOT mutated.