mnist 0.5.0

# MNIST
A crate for parsing the [MNIST](http://yann.lecun.com/exdb/mnist/) and [Fashion MNIST](https://github.com/zalandoresearch/fashion-mnist) data set into vectors to be
used by Rust programs.

* [Crate](https://crates.io/crates/mnist)
* [Documentation](https://docs.rs/mnist)

## Example
```rust
use mnist::*;
use ndarray::prelude::*;

fn main() {

    // Deconstruct the returned Mnist struct.
    let Mnist {
        trn_img,
        trn_lbl,
        tst_img,
     tst_lbl,
        ..
    } = MnistBuilder::new()
        .label_format_digit()
        .training_set_length(50_000)
        .validation_set_length(10_000)
        .test_set_length(10_000)
        .finalize();

    let image_num = 0;
    // Can use an Array2 or Array3 here (Array3 for visualization)
    let train_data = Array3::from_shape_vec((50_000, 28, 28), trn_img)
        .expect("Error converting images to Array3 struct")
        .map(|x| *x as f32 / 256.0);
    println!("{:#.1?}\n",train_data.slice(s![image_num, .., ..]));

    // Convert the returned Mnist struct to Array2 format
    let train_labels: Array2<f32> = Array2::from_shape_vec((50_000, 1), trn_lbl)
        .expect("Error converting training labels to Array2 struct")
        .map(|x| *x as f32);
    println!("The first digit is a {:?}",train_labels.slice(s![image_num, ..]) );

    let _test_data = Array3::from_shape_vec((10_000, 28, 28), tst_img)
        .expect("Error converting images to Array3 struct")
        .map(|x| *x as f32 / 256.);

    let _test_labels: Array2<f32> = Array2::from_shape_vec((10_000, 1), tst_lbl)
        .expect("Error converting testing labels to Array2 struct")
        .map(|x| *x as f32);
}
```

## Fashion MNIST
The Fasion MNIST [dataset](https://github.com/zalandoresearch/fashion-mnist) offers a similarly-formatted 
drop-in replacement dataset for the original MNIST set, but typically poses a more difficult classification challenge that handwritten numbers. 

An example of downloading this dataset may be found by running: 
```sh
$ cargo run --features download --example fashion_mnist
```