code: function createFunction (test, options) {
      return new DuckType({
        name: options && options.name || null,
        test: test
      });
    }
docs: Create a ducktype from a test function
  @param {Function} test   A test function, returning true when a provided
  object matches, or else returns false.
  @param {{name: String}} [options]
  @returns {*}