Description

Recently, I saw a student stuck after typing

io.imread('image.jpg', as_gray=True)

Silently, it loads as a RGB image.

Indeed, the API is as_grey. The problem is that our API is not homogeneous. It seems that US spelling is in majority in our library. I would suggest to either:

• make sure that both gray and grey are working
• raise a warning

Any suggestion @scikit-image/core ?