Ndarray dependency update

[pmalex]

Description

When using your crate in my example which uses the last ndarray version (0.16.1 at this point) cargo says

     |
163  |         let xs = mfcc(audio.view(), &SpeechConfig::default());
     |                  ---- ^^^^^^^^^^^^ expected `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>`, found a different `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>`
     |                  |
     |                  arguments to this function are incorrect
     |
     = note: `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>` and `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>` have similar names, but are actually distinct types
note: `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>` is defined in crate `ndarray`
    --> /home/alex/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ndarray-0.16.1/src/lib.rs:1280:1
     |
1280 | pub struct ArrayBase<S, D>
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^
note: `ArrayBase<ViewRepr<&f32>, Dim<[usize; 1]>>` is defined in crate `ndarray`
    --> /home/alex/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ndarray-0.15.6/src/lib.rs:1268:1
     |
1268 | pub struct ArrayBase<S, D>
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^
     = note: perhaps two different versions of crate `ndarray` are being used?
note: function defined here
    --> /home/alex/.cargo/git/checkouts/mfcc-rust-f366017b42cd793d/4cf3877/speechsauce/src/feature.rs:99:8
     |
99   | pub fn mfcc(signal: ArrayView1<f32>, speech_config: &SpeechConfig) -> Array2<f32> {
     |     

It seems that the problem is in using old version of ndarray and Cargo.toml in both subprojects should be updated, otherwise it impossible to use your crate with never ndarray versions.

DoD (Definition of Done)

• ndarray version in Cargo.toml updated
• crate successfully compiles