[gnome-backgrounds] add CC BY SA 2.0

[Jakub Steiner <jimmac src gnome org>]

commit 7d271396162343c38a4f9e5f1237032b993a3b6e
Author: Jakub Steiner <jimmac gmail com>
Date:   Wed Sep 3 19:31:06 2014 +0200

    add CC BY SA 2.0

 COPYING_CCBYSA2 |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/COPYING_CCBYSA2 b/COPYING_CCBYSA2
new file mode 100644
index 0000000..35a0849
--- /dev/null
+++ b/COPYING_CCBYSA2
@@ -0,0 +1,7 @@
+This work is licenced under the Creative Commons Attribution-Share Alike 2.0
+United States License. To view a copy of this licence, visit
+http://creativecommons.org/licenses/by-sa/2.0/ or send a letter to Creative
+Commons, 171 Second Street, Suite 300, San Francisco, California 94105, USA.
+
+When attributing the artwork, using "GNOME Project" is enough. 
+Please link to http://www.gnome.org where available.