Instantiation instructions in the readme are wrong

[brianpgerson]

Unless I'm misunderstanding something, you should update the readme to the following. Took me a bit of futzing around to figure it out for myself, because the current instructions did not work for me.

Updated:

To use with the default tld (.de):

var AmazonWishList = require('amazon-wish-list');
var awl = new AmazonWishList.default();

To use with another domain:

var AmazonWishList = require('amazon-wish-list');
var awl = new AmazonWishList.default(YOUR_TLD);

To see your list in the console (test ID is valid for .de only!):

awl.getById('NDDVVVWMJ6AN').then(function(list) {
  console.log(list);
});

BTW, happy to PR this myself if you'd prefer.