Bump to Rust 1.30, add macros to preludes, and switch macro_use to use

[jturner314]

This PR adds the array, azip, s, and par_azip macros to their respective crates' preludes. Where possible, it also replaces macro_use with normal use statements.

This requires Rust 1.30.

[bluss]

Oh it's beautiful. And those things now share the same namespace (or maybe equally named things are punned and both used, just like for newtype constructors).

[jturner314]

Yeah, this is so much cleaner than the old #[macro_use] annotations.

Macros have a separate namespace, and all equally named things are imported when used. (For example, use ndarray::stack; imports both the function and the macro.)

[bluss]

The short macro name of s might now be yet more risky, when it comes through the prelude. I think it will work in practice though.

[jturner314]

I just added another commit that makes it possible to use s! and azip! without importing them. (You can now write ndarray::s![1..2, ..], for example.)

The short macro name of s might now be yet more risky, when it comes through the prelude. I think it will work in practice though.

Yeah, I think it'll be fine because (1) macros are in a separate namespace from variables/functions, (2) a short name like s seems very unusual for a macro, and (3) macros are evaluated at compile time, so potential issues will be caught at compile time.

[bluss]

Towards the future, breaking change season is here