Release version 3.0.0

This release brings compatibility with TYPO3 8.1, and other improvements:

* TYPO3 8.1 compatibility
* Add `List-Unsubscribe` header, so end-users can easily unsubscribe
* Add `Precedence: bulk` header, to follow Gmail guidelines
* Inject `alt` attributes when missing from <img> element
* Significantly improves speed for email opening, link opening and bounce handling
* Better error reporting when the content cannot be fetched

And [all known bugs were fixed](https://github.com/Ecodev/newsletter/issues?q=milestone%3A3.0%20%20)

BREAKING CHANGES
================

* Requires PHP 5.6 or higher with `dom` extension
* Database structure changed and must be updated
* Existing data in DB **must** be updated. Use the "update" button in Extension Manager.

ext_emconf.php

@@ -5,7 +5,7 @@
     'description' => 'Send any pages as Newsletter and provide statistics on opened emails and clicked links.',
     'category' => 'module',
     'shy' => 0,
-    'version' => '2.6.1',
+    'version' => '3.0.0',
     'dependencies' => '',
     'conflicts' => '',
     'priority' => '',