* added: `get_server_information()`
  * changed: Urgency is now an enum
  * changed: pack methods return actual empty arrays now (builds with 1.0.0)
  * changed: moved to dbus-rs 0.1.0
  * changed: moved examples into tests
  * changed: made `get_capabilities()` global
  * changed: made `exe_name()` private
  * elaborated documentation