Add and use Karbor beaver mascot

Change-Id: Ic208d19032b61b8bfa5ba34bb0763573cbe4e355

README.rst

@@ -13,7 +13,7 @@ Karbor
 
 Application Data Protection as a Service for OpenStack
 
-.. image:: https://raw.githubusercontent.com/openstack/karbor/master/doc/images/Karbor.png
+.. image:: https://raw.githubusercontent.com/openstack/karbor/master/doc/images/mascot/OpenStack_Project_Karbor_vertical.png
     :alt: Karbor
     :width: 300
     :height: 525
@@ -58,12 +58,6 @@ Links
 * Source: http://git.openstack.org/cgit/openstack/karbor
 * Bugs: http://bugs.launchpad.net/karbor
 
-.. image:: https://raw.githubusercontent.com/openstack/karbor/master/doc/images/KarborInPieces.png
-    :alt: Karbor
-    :width: 200
-    :height: 525
-    :align: center
-
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 Features
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