## MutableX
Create X-sized mutable signals for FutureSignals.
### Usage
From [tests/basic.rs](/tests/basic.rs)
```rs
#[cfg(test)]
pub mod test {
use futures_signals::signal::{Mutable, SignalExt};
use mutablex::mutable_x;
#[test]
pub fn basic() {
mutable_x!(2);
let stream_a = Mutable::new(1);
let stream_b = Mutable::new(2);
let combination = Mutable2::new(stream_a.clone(), stream_b.clone());
let _ = combination.map(|(a, b)| {
println!("{} {}", a, b);
});
stream_a.set(3);
stream_b.set(4);
}
}
```