Prepare for 0.4.0 (#42)

Changelog.md

@@ -2,11 +2,18 @@
 
 This document will tell you what changes that has been made between versions.
 
+# Changes from 0.3.x to 0.4.0
+
+* Removed `mailgun.library` service and `mailgun.swift_transport.transport.class` parameter.
+* Improved testing
+* Avoid usage of deprecated Mailgun functions. 
+
+
 # Changes from 0.2.x to 0.3.0
 
 * Upgraded from Mailgun client 1.x to 2.x.
 * Start using PSR-4
 * Improved tests and documentation
 * Changed namespace of `cspoo\Swiftmailer\MailgunBundle\Services\MailgunTransport` to `cspoo\Swiftmailer\MailgunBundle\Service\MailgunTransport`
 * Catching all exception that may be thrown by the MailGun API.
-* The return value of MaingunTransport::sendMessage is no longer fixed to 1. It does now comply with the interface.
+* The return value of MaingunTransport::sendMessage is no longer fixed to 1. It does now comply with the interface.