Update Guzzle to 7 (#311)

* Fixes #306 with update to Guzzle 7
* Update SendMail test, closes #310

Author: MIchaelMainer

composer.json

@@ -13,7 +13,7 @@
 	],
 	"require": {
 		"php": "^7.1",
-		"guzzlehttp/guzzle": "^6.2"
+		"guzzlehttp/guzzle": "^7.0"
 	},
 	"require-dev": {
 		"phpunit/phpunit": "^7.5",

tests/Functional/MailTest.php

@@ -42,15 +42,17 @@ public function createEmail($emailBody)
     */
     public function testSendMail()
     {
-        $message = $this->createEmail("Sent from the SendMail test");
+        $message = $this->createEmail("Sent from the SendMail test - Técnica");
 
         $body = array("message" => $message);
 
         $this->_client->createRequest("POST", "/me/sendmail")
                       ->attachBody($body)
                       ->execute();
 
-        $mailFolderMessages = $this->_client->createRequest("GET", "/me/mailFolders/sentItems/messages?\$filter=subject eq '\$message->getSubject()'")
+        $subject = $message->getSubject();
+
+        $mailFolderMessages = $this->_client->createRequest("GET", "/me/mailFolders/sentItems/messages?\$filter=subject eq '$subject'")
                                             ->setReturnType(Model\Message::class)
                                             ->execute();
         $this->assertNotNull($mailFolderMessages);