* Add settings option to enable/disable automatically showing tip box
* Add public `check_state()` method to `Bitcointips` class to modularize things
* Add public `show_widget()` method to `Bitcointips` class for use with new shortcode
* Add public `get_stats()` method to `Bitcointips` class for use with the new shortcode
* Add public `the_post_address()` method to `Bitcointips` class for use with the new shortcode
* Add `bitcointips_shortcde()` function for new `[bitcointips]` WordPress shortcode