isflattenable

Republish of lodash internal isflattenable method.

var isFlattenable = require('isflattenable');
var assert = require('assert');

var array1 = [1, [2, [3, [4]], 5]];
assert.ok(isFlattenable(array1));

// Republished from lodash https://github.com/lodash/lodash/blob/master/.internal/isFlattenable.js