Reinstate tifffile_plugin for backwards compatibility

skimage/io/_plugins/tifffile_plugin.ini

@@ -0,0 +1,3 @@
+[tifffile]
+description = Load and save TIFF and TIFF-based images using tifffile.py
+provides = imread, imsave

skimage/io/_plugins/tifffile_plugin.py

@@ -0,0 +1,6 @@
+try:
+    from tifffile import imread, imsave
+except ImportError:
+    raise ImportError("The tifffile module could not be found.\n"
+        "It can be obtained at "
+        "<http://www.lfd.uci.edu/~gohlke/code/tifffile.py>\n")