Names of functions about imageio

[ghisvail]

imsave -> imwrite, this change does not shock me at all. Besides, I believe that's the convention used in MATLAB, so this change is likely to make the transition easier for anyone coming from it.

imageio.write(...) looks and should act as a function. If this has to return something, it might be the size of the buffer written, an error code, or simply a boolean for success / failure. A different approach could be to use a context manager paired with a with statement.

It is also good to provide an object-oriented option with the Writer interface. An appropriate factory method, whereby the file type is inferred from the arguments, sounds like a good solution to me for the time being. You might want to use a more complex pattern later if need be.

[almarklein]

Done