Rank filters

Hi everyone, We just merged an exciting new rank filtering module, implemented by Olivier Debeir and guided through review by Johannes Schönberger. These filters work on the principle that, as a sliding window moves over an image, its histogram can be efficiently updated by considering only new values introduced (and left behind) by the moving footprint. Here are some examples from the gallery: http://scikit-image.org/docs/dev/auto_examples/applications/plot_rank_filter... Enjoy! Stéfan