Modify mpl_image_to_rgba to allow RGB input image

mpl_image_to_rgba produces a image of shape (M, N, 3, 4) when the input
image is already RGB. This is understandably confusing for downstream
processes, and this commit fixes it.
Merge pull request #802 from jni/allow-rgb-save

Modify mpl_image_to_rgba to allow RGB input image
Add deconvolution module to skimage.

This module add three function to skimage. The `wiener` function is a
simple wiener deconvolution. The `unsupervised_wiener` is a more
sophisticated wiener deconvolution with automatic estimation of
regularisation parameters. The third function is a literal traduction
in python of the rychardson lucy deconvolution of wikipedia.
Rename test to tests
Some improvements to new deconvolution code
Remove anfft and fftw dependency
Use assert_allclose for testing.
Remove __author__ line and add in CONTRIBUTORS.txt
Change copyright to scikit-image team
Add a small note explaining the wiener filter.
Add pdf paper
Inline crandn function.
Whitespace...
Fix the bad results of unsupervised deconvolution.

The initial implementation was simplified to reduce the number of
local variable. Consequently the parameter data.size was wrong. It was
the size of the fourier spectrum, with hermitian property, instead of
the real space size. This should work.

In addition the PSF is now normalized.
Typo fix.
Add test for Richardson Lucy.
Add the reference image for Richardson Lucy test.
Fix example.
Fix relative uft import for travis-ci pass
You shall not pass !