add user guide parallelization
Comments of the PR
Move canny from filter to feature
remove auto added __author__ in __init__.py file
ENH: Simplify marching_cubes for maintainability.

This does not change execution time, but the entire algorithm
is much simpler to read and understand without the branching
Cython code paths for anisotropic inputs. Memory usage decreases
a minor amount.
fix wrong version number
update api_changes
Added gitwash as an option on the makefile.
Updated the gitwash build.
fix import inside documentation and update TODO
fix import in filter.__init__
move import to avoid infinte recursion (filter import peak that import feature that import filter)
Canny is now deprecated and will be in api_changes in v0.13
Fixes a bug in _update_doc in skimage/io/__init__.py that will attempt to compute max of empty list if no plugins are found.
hack to avoid circular import when import canny
Modified rank filters package so that the _core function in core.pyx outputs to a 3D image, permitting the generation of images with arbitrary size feature vector pixels. Implemented windowed_histogram that generates a windowed histogram of an image.
Fixed some test failures and added a test for windowed_histogram.
Fixed some issues with the new windowed_histogram function in filter.rank.
It used to be able to output uint8 histogram, whose max pixel counts of 255 could easily overflow. Addressed by limiting the output type to float.
Normalized histograms are now generated, otherwise behaviour is unpredictable at boundaries or when pixels are not permitted by a mask.
The new optional n_bins parameter allows the caller to specify the size of the histogram generated. Having it fixed to image.max()+1 could result in feature vectors being shorter than desired just due to a value not being used in an image.
An example has been added to the docs, that demonstrates the application of windows histograms in object matching; a single coin is extracted and found by chi squared histogram matching.
Move handling of blit behavior to axes object.
Push handling of line tools to axes level for better coordination.