tokio-scoped 0.1.0

# tokio-scoped
tokio-scoped provides a `scope` function and `ScopedRuntime` struct inspired by [crossbeam](https://docs.rs/crossbeam/0.4.1/crossbeam/fn.scope.html)
but for the `tokio` Runtime. A scope allows one to spawn futures which do not have a `'static` lifetime
by ensuring each future spawned in the scope completes before the scope exits.

## Example

```rust
# extern crate tokio_scoped;
# extern crate futures;
# use futures::lazy;

let mut v = String::from("Hello");
tokio_scoped::scope(|scope| {
    // Use the scope to spawn the future.
    scope.spawn(lazy(|| {
        v.push('!');
        Ok(())
    }));
});
// The scope won't exit until all spawned futures are complete.
assert_eq!(v.as_str(), "Hello!");
```