Documenting inherited methods and attributes can lead to overly verbose docs. For example, the `Image` class, which subclasses ndarray, and various viewer-related classes, which subclass PyQt and Matplotlib classes, have hundreds of irrelevant methods added to the API docs.
Either the role should be removed (as done here) or the inheritance-diagram extension needs to be added to the config file. Since skimage doesn't have a complicated class hierarchies, it's probably best to remove.
__import__ can get confused about which scikits path to import when multiple scikits are present on a system.
Note that `root_module` is no longer an attribute of `ApiDocWriter` (it wasn't being used anywhere), and it now points to "scikits.image" instead of "scikits".
Tony S Yu