complex in Rust

Creates complex numbers of type num::complex::Complex. Both the real and imaginary part of the complex number must be of the same type.
```
fn main() {
    let complex_integer = num::complex::Complex::new(10, 20);
    let complex_float = num::complex::Complex::new(10.1, 20.1);

    println!("Complex integer: {}", complex_integer);
    println!("Complex float: {}", complex_float);
```