Small fixes (#81)

* PHPUnit > Add `name` attribute to `testsuite` element

* Bump minimum `jms/serializer` version

* Bump minimum `simple-bus/message-bus` version

* Fix wrong version constraint

Author: ruudk

phpunit.xml.dist

@@ -16,7 +16,7 @@
     </php>
 
     <testsuites>
-        <testsuite>
+        <testsuite name="Everything">
             <directory>./tests/</directory>
         </testsuite>
     </testsuites>