* More examples
* Look at the unwind safety and unwinding in general.
* Something like select
* Wait for future with timeout?
* Can we rely on *any* future executor?
* Iterator that leaves the rest there on break
* leak_on_panic support
* Spawn one future per coroutine (possibly lazily) that just delegates to
whatever is being waited on right now instead of spawning one for every
waited thing. Challeng: how to resolve it once the coroutine ends?
* Update README