complete singularization of scikit-image

I've updated references in the code and documentation to the new name.
Merge pull request #359 from ivanov/singular-scikit

PKG: Complete singularization of scikit-image.
DOC: Clean up one last skimage -> scikit-image.
PKG: Print something when bento check passes.
DOC: Add imports to doctests to fix errors
Merge pull request #360 from tonysyu/fix-doctest-imports

DOC: Add imports to doctests to fix errors
Add note about random test failure for some systems
Split tests for different channel numbers into separate functions
Add missing empty lines between test functions
DOC: Fix pip command.
DOC: Add imports to doctests to fix errors
Add support for 3-dimensional image resizing
Split 3d resize test function
Merge pull request #293 from ahojnnes/resample

ENH: Add support for 3-dimensional image resizing.
Merge pull request #351 from ahojnnes/test-coverage

Test coverage
Fix failing perimeter test caused by bug in scipy
Merge pull request #362 from ahojnnes/perimeter-test

BUG: Fix failing perimeter test caused by bug in scipy.
add ref
add comment to bilateral denoising example
compare local and global equalise in example