Confusing Features

[akern40]

ndarray currently has an empty test feature and a docs feature that combines approx, serde, and rayon. My feeling is that these are red herrings, in a way: they describe compilations that we as the developers might like, but not the end users. I worry that it muddies the waters for new users and doesn't conform to Rust's "explicit" mindset. Would people be open to removing these feature flags?