Bump to version 0.5.0

Version 0.5.0 includes some new features.

New features:

* Add workaround for Spotify to get metadata
* Add `position` cli command to query and set position
* Add `position` property to Player and method to set position to
library

configure.ac

@@ -1,6 +1,6 @@
 m4_define([playerctl_major_version], [0])
-m4_define([playerctl_minor_version], [4])
-m4_define([playerctl_micro_version], [2])
+m4_define([playerctl_minor_version], [5])
+m4_define([playerctl_micro_version], [0])
 
 m4_define([playerctl_version], [playerctl_major_version.playerctl_minor_version.playerctl_micro_version])