Utility for random grouping.
The author of this crate is not good at English.
Forgive me if the document is hard to read.
This is useful for grouping multiple items into some groups at random.
```rust
let mut rg = RandomGrouping::new();
let samples = (0..10).collect::
let result = rg.dividebyratio(&samples, &ratios);
assert!(result.len() == ratios.len()); for i in 0..result.len() { let groupsize = (ratios[i] * samples.len() as f64).floor() as usize; assert!(result[i].len() == groupsize); assert!(result[i].iter().all(|x| samples.contains(x))); } ```