[MRG+1] Insert metadata in docstrings of images in skimage.data.*

[sciunto]

This PR solves the first item of #989 with the recommendation of @stefanv #993 (comment)

I used a similar function name as in regionprops.

This screenshot illustrates the result. I'm open to comments, especially on the style we want...

Cc @cdeil

[codecov-io]

Current coverage is 90.66% (diff: 100%)

Merging #2236 into master will increase coverage by 0.06%

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[jni]

I don't think I'm a fan of this approach. What if we want to add new functions? It's up to the contributor to figure out that this global function is messing with their contribution.

Instead, I would suggest a decorator that gets applied to each image function. It's a bit more wordy, but also more self-documenting.

As an alternative, I would make this list explicit, instead of implicitly loading all names.

[stefanv]

I don't think we can do this, since it requires loading all images upon import.

Can we just hardcode the meta-data?

[sciunto]

ok. Do you have a preferred format? (Just to make it right with a single bullet :) )

[sciunto]

function to print metadata.

def f():
    from skimage import data
    import sys
    for name in data.__all__:
        if name in ('load', 'lena'):
            continue
        func = getattr(sys.modules[data.__name__], name)
        metadata = "    Shape: %s; dtype: %s" % (func().shape, func().dtype)
        print(name)
        print(metadata)

[sciunto]

I inserted manually the metadata. I posted a code to double check.

[soupault]

Looks good.

[sciunto]

Looks like the random travis failures are due to #2237

[emmanuelle]

Travis is now happy: merging!