fix compile error

Author: bbottema

src/test/java/demo/MailTestApp.java

@@ -2,8 +2,8 @@
 
 import org.simplejavamail.email.Email;
 import org.simplejavamail.mailer.Mailer;
-import org.simplejavamail.mailer.ServerConfig;
-import org.simplejavamail.mailer.TransportStrategy;
+import org.simplejavamail.mailer.config.ServerConfig;
+import org.simplejavamail.mailer.config.TransportStrategy;
 import testutil.ConfigLoaderTestHelper;
 
 import javax.mail.Message.RecipientType;