JuliaImages
Fix and test clustering
This has one breaking change: while the docs advertise that
"All the segmentation algorithms (except Fuzzy C-means) return a
struct SegmentedImage," that's not been true for kmeans.
This changes the output so that kmeans does return a SegmentedImage.
This is a breaking change, because the types are not interchangeable.
This became apparent when trying to add tests for kmeans, which
have been lacking.
Before releasing this, we may want to make a second breaking change:
currently, ImageSegmentation provides a new meaning for
Matrix{Gray{T}} than Clustering.jl provides for Matrix{T}.
This breaks our abstraction that Gray ≈ Number.
A way to fix that would be to have ImageSegmentation.kmeans
be a different function from Clustering.kmeans, and obviously
have the one in ImageSegmentation call the one in Clustering.
