Re-export image

[cospectrum]

The problem is described here.

This gives the user the ability to not depend on image, so the code will always compile.
Once this version of imageproc is published on crates.io, we can add use imageproc::image to the beginning of all examples.

[theotherphil]

Ah, neat - I haven’t come across this before. Thanks.

I’ll publish a new crate version tomorrow.

[cospectrum]

Ah, neat - I haven’t come across this before. Thanks.

I’ll publish a new crate version tomorrow.

Yes, I already see people trying to use image 0.25 with imageproc, but it doesn't compile.

About reexport. I'm wondering if we should add more image features. Because without "image/default", some examples will panic (decoding PNG or other formats) if imageproc::image is used.