* 2.4.0 (2016-10-09)

 * added support for setLocalDomain() and setStreamOptions()
 * updated the styles of the SwiftMailer commands
 * removed support for deprecated versions of Symfony
 * added support for LoadBalancedTransport in SendEmailCommand
 * fixed messagePart.charset not defined in the web profiler
 * fixed performance on Symfony 3 (IntrospectableContainerInterface does not exist anymore)
 * allowed empty transport configs
 * added a priority flag on plugins tag
