Calculate the greatest common divisor of multiple values
```rust use gcdx::gcdx;
fn main() { let v: Vec = vec![10, 9, 8, 7]; let g = gcdx(v).unwrap(); println!("{}", g); assert_eq!(g, 1);
let v: Vec<u32> = vec![10, 9, 8, 7]; let g = gcdx(v).unwrap(); println!("{}", g); assert_eq!(g, 1);
} ```