I/O infrastructure

[Stéfan van der Walt]

Hi all,

Juan recently again brought to my attention the dismal state of the
scikit-image I/O infrastructure.  This needs to be fixed for 0.11
(0.10 is almost out the door--this weekend, I hope!).

We are currently relying on other libraries to do the job, and while
it allows you to do "from skimage import io; io.imread(anything)" on
almost any platform, it's just not working--we need reproducible
backends.

My current thinking is thus: make Luis's "imread" [0] a dependency,
and remove all plugins from scikit-image.  Users can, of course, still
load data using mpl, imread, astropy or whatever suits them.  In the
documentation, we may provide recipes for handling files like ITK,
gdal etc. if that proves useful.

What do you think?

Stéfan

[0] https://github.com/luispedro/imread