New release: 1.3
    
    - Document differences between dasbus and pydbus (vponcova)
    - Improve the support for interface proxies in the service identifier (vponcova)
    - Improve the support for interface proxies in the message bus (vponcova)
    - Test the interface proxies (vponcova)
    - Make the message bus of a service identifier accessible (vponcova)
    - Fix the testing environment for Fedora Rawhide (vponcova)