New animation example inspired from the Joy Division's Unchained Love cover
bug fix: check the type of the 'key' of the two array 'r1' and 'r2'
Error message written in proper English
Merge pull request #3111 from montefra/mlab_bug

bug fix: check the type of the 'key' of the two array 'r1' and 'r2'
Merge pull request #3099 from rougier/unchained

New animation example (Joy Division's Unchained Love cover)
DOC : fixed urls

 - fixed removed explicit matplotlib.org when relative link will do
 - fixed up moved examples
Adding Colorbar.remove()