remove unused social media logos and add attribution

COPYRIGHT

@@ -21,3 +21,8 @@ exception to your version of the file(s), but you are not obligated to
 do so.  If you do not wish to do so, delete this exception statement from your
 version.  If you delete this exception statement from all source files in the
 program, then also delete it here.
+
+Social Media Icons
+------------------
+Some icons are used from https://github.com/paulrobertlloyd/socialmediaicons
+Licensed under a Creative Commons Attribution-Share Alike 3.0 license

app/assets/images/social_media_logos/Readme.txt

+Social Media Icons from https://github.com/paulrobertlloyd/socialmediaicons
+
+Licensed under a Creative Commons Attribution-Share Alike 3.0 license