Add a little bit of padding between caret and menu item text.
Move the buildMenu() from Dropdown method to plain function

This is to remove it from Dropdown public API.
Also, call it conditionally if menuOptions option is set, to allow for manually placing the menu in the markup.
Fix addEventListener function comments.
Fix the Dropdown.prototype.toggle method to allow it to be called on the instance
Change implementation example to two examples: one with a dynamically generated menu from JS object, and another with a fixed menu placed in the markup