function _dispatchable(methodNames, transducerCreator, fn) {
    return function () {
      if (arguments.length === 0) {
        return fn();
      }
      var obj = arguments[arguments.length - 1];
      if (!_isArray(obj)) {
        var idx = 0;
        while (idx < methodNames.length) {
          if (typeof obj[methodNames[idx]] === 'function') {
            return obj[methodNames[idx]].apply(obj, Array.prototype.slice.call(arguments, 0, -1));
          }
          idx += 1;
        }
        if (_isTransformer(obj)) {
          var transducer = transducerCreator.apply(null, Array.prototype.slice.call(arguments, 0, -1));
          return transducer(obj);
        }
      }
      return fn.apply(this, arguments);
    };
  }
Returns a function that dispatches with different strategies based on the
object in list position (last argument). If it is an array, executes [fn].
Otherwise, if it has a function with one of the given method names, it will
execute that function (functor case). Otherwise, if it is a transformer,
uses transducer created by [transducerCreator] to return a new transformer
(transducer case).
Otherwise, it will default to executing [fn].

@private
@param {Array} methodNames properties to check for a custom implementation
@param {Function} transducerCreator transducer factory if object is transformer
@param {Function} fn default ramda implementation
@return {Function} A function that dispatches on object in list position