[gnome-nibbles] Bump Gtk+ required version to 3.15.0.

[Arnaud Bonatti <arnaudb src gnome org>]

commit 9dfc94778e8a982fa532e02887378c8cb904b746
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Fri Feb 20 20:36:44 2015 +0100

    Bump Gtk+ required version to 3.15.0.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index fd8343a..8810d42 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,7 +17,7 @@ dnl ###########################################################################
 dnl Dependencies
 dnl ###########################################################################
 
-GTK_REQUIRED=3.12.0
+GTK_REQUIRED=3.15.0
 RSVG_REQUIRED=2.32.0
 CANBERRA_GTK_REQUIRED=0.26
 CLUTTER_REQUIRED=1.14.4