The Events Calendar - Community Events 4.10.17

* Fix - Prevent multiple notification emails from being sent every time an already-submitted event is edited (thanks to @proactivedesign in the forums for flagging this bug!)
* Fix - Fixed JavaScript error with datepickers on small viewport sizes
* Tweak - Fixed some misalignment of buttons above Community Events' front-end "My Events" list in the Twenty Seventeen theme

* Feature - Added updater class to enable changes on future updates
* Fix - Prevented errors under PHP 7.2 in relation to the use of `create_function`
* Fix - Restored the ability of community organizers to email the attendee list, even if they are blocked from accessing the admin environment (thanks to mindaji in our forums for reporting this)

* Fix - Prevent the loss of event start date, end date, start time, end time, "all day" event, and timezone choices upon failed event submission (thanks to @netdesign and many others for highlighting this issue) [94010]
* Fix - Fixed additional fields from Events Calendar PRO on the event-submission form so that their values are saved upon a failed form submission (thanks @myrunningresource for flagging this bug!) [94908]
* Tweak - Fixed misalignment of "Display Options" button in the front-end "My Events" list [93521]
* Tweak - Adjust the edit-organizer and edit-venue form styles to make both forms more readable (props @artcantina for highlighting these issues) [95043]