BUG-FIX: update colorbar when chaning image
Use blit to speed up image drawing
BUG-FIX: errors were raised when hovering the mouse pointer over an image axis where there is no image data
BUG-FIX: when updating the image the optimized vmax and vmin were not used
BUG-FIX: the colorbar colors were not updated what was a problem when the first image of a set had no constrast
Merge pull request #97 from francisco-dlp/ENH_image_plotting

Enh image plotting