Added sections to gallery of examples

Modified travis_script.sh to account for the new structure of the gallery

Added README.txt files in directories of gallery examples

Fixed references to gallery images in user guide pages

Fixed broken links

doc/examples/segmentation/plot_ncut.py

@@ -0,0 +1,33 @@
+"""
+==============
+Normalized Cut
+==============
+
+This example constructs a Region Adjacency Graph (RAG) and recursively performs
+a Normalized Cut on it.
+
+References
+----------
+.. [1] Shi, J.; Malik, J., "Normalized cuts and image segmentation",
+       Pattern Analysis and Machine Intelligence,
+       IEEE Transactions on, vol. 22, no. 8, pp. 888-905, August 2000.
+"""
+from skimage import data, io, segmentation, color
+from skimage.future import graph
+from matplotlib import pyplot as plt
+
+
+img = data.coffee()
+
+labels1 = segmentation.slic(img, compactness=30, n_segments=400)
+out1 = color.label2rgb(labels1, img, kind='avg')
+
+g = graph.rag_mean_color(img, labels1, mode='similarity')
+labels2 = graph.cut_normalized(labels1, g)
+out2 = color.label2rgb(labels2, img, kind='avg')
+
+plt.figure()
+io.imshow(out1)
+plt.figure()
+io.imshow(out2)
+io.show()