Prepare release v0.4.0

Signed-off-by: Christian Heimes <cheimes@redhat.com>

Author: tiran

src/custodia/__about__.py

@@ -9,7 +9,7 @@
 __summary__ = 'A service to manage, retrieve and store secrets.'
 __uri__ = 'https://github.com/latchset/custodia'
 
-__version_info__ = (0, 4, 'dev2')
+__version_info__ = (0, 4, 0)
 __version__ = '.'.join(str(v) for v in __version_info__)
 
 __author__ = 'Custodia project Contributors'