update, get_date, set_date methods are not working

The methods `update`, `get_date`, `set_date` are not working in the latest version of library. It happened after [this commit](https://github.com/nazar-pc/PickMeUp/commit/3f846c7cac1a4663f31c300edcb4f08383f29047). It seems like accidentally `'pickmeup-options'` data attribute was replaced with incorrect one `'pickmeup-initial_options'`.  The pull-request resolves the issue.