Set Stream types as must_use

src/reactor/interval.rs

@@ -21,6 +21,7 @@ use reactor::timeout_token::TimeoutToken;
 /// Note that timeouts are not intended for high resolution timers, but rather
 /// they will likely fire some granularity after the exact instant that they're
 /// otherwise indicated to fire at.
+#[must_use = "streams do nothing unless polled"]
 pub struct Interval {
     token: TimeoutToken,
     next: Instant,