Switch logo to SVG version, add attribution

Attribution required by CC-BY 2.5 license.

<img/> hack to workaround isaacs/github#316 .

contrib/jabber/README.md

@@ -9,7 +9,7 @@
 <!-- markdown-toc end -->
 # Jabber contribution layer for Spacemacs
 
-![logo](img/jabber-logo.gif)
+<img src="img/Jabber_logo.svg"></img>
 
 
 ## Description

contrib/jabber/img/attribution.md

@@ -0,0 +1,11 @@
+This image (Jabber_logo.svg) was created by Wikimedia Commons users
+[Sven](http://commons.wikimedia.org/wiki/User:Sven) and
+[D0ktorz](http://commons.wikimedia.org/wiki/User:D0ktorz) and is
+available
+[at Wikimedia Commons](http://commons.wikimedia.org/wiki/File:Jabber_logo.svg)
+under the
+[CC-BY 2.5 license](http://creativecommons.org/licenses/by/2.5/).  It
+is a derivative of the original Jabber logo as copyrighted and owned
+by the Jabber Software Foundation, which is also released under CC-BY
+2.5 and is available at
+[at Wikimedia Commons](http://commons.wikimedia.org/wiki/File:Jabber_logo.png).