finalized logo

- use the ZAG version of the logo (same as used for blog post in
  PR MDAnalysis/MDAnalysis.github.io#207 )
- updated AUTHOR

docs/rst/_static/logos/AUTHOR

@@ -1,16 +1,21 @@
-The MDAnalysis 'Atom' logo was created by Christian Beckstein and is
+The original MDAnalysis 'Atom' logo was created by Christian Beckstein.
+The mdacli logo is a derivative of the 'Atom' logo and is
 
-Copyright (c) 2011 Christian Beckstein
+Copyright (c) 2021 "The MDAnalysis Development Team and NumFOCUS"
 
-MDAnalysis Logo 'Atom' by Christian Beckstein is licensed under a
+mdacli logo is made available under a
 Creative Commons Attribution-NoDerivs 3.0 Unported License.
 To view a copy of this license, visit
 http://creativecommons.org/licenses/by-nd/3.0/ or send a letter to Creative
 Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.
 
-The logo is contained in the file 'mdanalysis-logo.png'.
+The mdacli logo is contained in the files
+
+mdacli-logo-square.pdf  
+mdacli-logo-square.png  
+mdacli-logo.pdf  
+mdacli-logo.png
+
+The mdanalysis-logo.ico file is a version of the MDAnalysis 'Atom' logo, which
+is also made available under CC-BY-ND 3.0.
 
-Derivatives in the files 'mdanalysis-logo-127x55.png',
-'mdanalysis-logo-200x150.png', 'mdanalysis-logo.ico' were created for
-inclusion in MDAnalysis and on websites related to MDAnalysis. They
-are distributed under the same license as the 'Atom' logo.