Tweak segmentation parameters in solution

For some reason active_contour and random_walker return different
results now. Earlier dependencies were not tested. The results with
tweaked active_contour and random_walker (as before excpect for fixed
indexing) are similar if slightly worse than before.

lectures/solutions/4_segmentation.ipynb

@@ -361,7 +361,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "snake = seg.active_contour(astronaut_gray, points, alpha=0.1, w_edge=1.3)"
+    "snake = seg.active_contour(astronaut_gray, points, alpha=0.1)"
    ]
   },
   {
@@ -459,7 +459,7 @@
     "indices = draw.circle_perimeter(100, 220, 25)\n",
     "\n",
     "astronaut_labels[indices] = 1\n",
-    "astronaut_labels[points[:, 1].astype(np.int), points[:, 0].astype(np.int)] = 2\n",
+    "astronaut_labels[points[:, 0].astype(int), points[:, 1].astype(int)] = 2\n",
     "\n",
     "image_show(astronaut_labels);"
    ]