message: updated mention of `loadFromDirectory` api
diff: @@ -72,7 +72,7 @@ to load images from:
  ```js
  template.keys("/etc/passbook/keys", "secret");
  -template.loadImagesFrom("images");
  +template.images.loadFromDirectory("images");
  ```
  The last part is optional, but if you have images that are common to all passes,
  