Merge pull request #136 from stefanv/plugin_consistency

ENH: Plugin consistency.

skimage/io/__init__.py

@@ -10,7 +10,7 @@ from ._plugins import info as plugin_info
 from ._plugins import configuration as plugin_order
 available_plugins = plugins()
 
-for preferred_plugin in ['pil', 'matplotlib', 'qt', 'null']:
+for preferred_plugin in ['matplotlib', 'pil', 'qt', 'null']:
     if preferred_plugin in available_plugins:
         try:
             use_plugin(preferred_plugin)

skimage/io/_plugins/pil_plugin.ini

@@ -1,4 +1,3 @@
 [pil]
 description = Image reading via the Python Imaging Library
-provides = imread, imsave, imshow
-
+provides = imread, imsave, imshow, _app_show

skimage/io/_plugins/pil_plugin.py

@@ -111,3 +111,6 @@ def imshow(arr):
 
     """
     Image.fromarray(img_as_ubyte(arr)).show()
+
+def _app_show():
+    pass