Create random integer provider

[vianneybacoup]

Implement #17

[hugues31]

@vianneybacoup could you please add a few lines regarding the integer provider on our docs ? 😃

[vianneybacoup]

@vianneybacoup could you please add a few lines regarding the integer provider on our docs ? 😃

Done, you can review !

[hugues31]

Perfect, I merge :)

[hugues31]

I think we could try this syntax :

let yaml_min = min.map_or(String::new(), |value| format!("\nmin: {}", value));
let yaml_max = max.map_or(String::new(), |value| format!("\nmax: {}", value));