[caribou] Initialize Clutter explicitly in antler code.

[Parag Nemade <panemade src gnome org>]

commit cfa18dcf608e10e01e6074ae39bd6bfeb9842229
Author: Parag Nemade <pnemade redhat com>
Date:   Sun Jul 3 13:12:44 2016 +0530

    Initialize Clutter explicitly in antler code.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=768104

 caribou/antler/window.py |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/caribou/antler/window.py b/caribou/antler/window.py
index 980869a..09d770a 100644
--- a/caribou/antler/window.py
+++ b/caribou/antler/window.py
@@ -45,6 +45,8 @@ class AnimatedWindowBase(Gtk.Window, Clutter.Animatable):
         }
     def __init__(self):
         GObject.GObject.__init__(self, type=Gtk.WindowType.POPUP)
+        Clutter.init(None)
+
         # animation
         self._stage = Clutter.Stage.get_default()
         self._move_animation = None