The Events Calendar - Eventbrite Tickets 4.6.15

* Feature - Add check and enforce PHP 5.6 as the minimum version [116282]
* Feature - Add system to check plugin versions to inform you to update and prevent site breaking errors [116841]
* Tweak - Added filters: `tribe_not_php_version_names`
* Deprecated - The constant `REQUIRED_TEC_VERSION`, `init_addon()` and `register_active_plugin()` method has been deprecated in `Tribe__Events__Tickets__Eventbrite__Main` in favor of Plugin Dependency Checking system
* Deprecated - The `tribe_events_eventbrite_start()`, `Tribe_Eventbrite_Load()`, `eventbrite_setup_textdomain()`, and `tribe_events_eventbrite_activate()` in favor of new Dependency Checking System
* Language - 7 new strings added, 52 updated, 0 fuzzied, and 0 obsoleted

* Fix - Eventbrite tickets not appearing on the event frontend
* Fix - Ensure that looking up an event's Eventbrite.com ID via get_post_meta() does not interfere with other plugins' and themes' post meta lookups
* Tweak - Ensure the "is migrating" transient and admin notice don't persist indefinitely
* Language - 0 new strings added, 46 updated, 0 fuzzied, and 0 obsoleted

* Fix - Prevent the "Use image on Eventbrite.com?" checkbox from showing up on non-Event post types [116215]
* Tweak - Update Eventbrite branding images to use their new logo and wordmarks [115661]