Revert "util: implement stream debounce combinator (#747)" (#834)

This reverts commit 7a49ebb.

The commit conflicted with another change that was merged, causing CI to fail. The public API
also requires a bit more refinement (#833) and Tokio crates need to be released.

src/util/stream.rs

@@ -1,8 +1,7 @@
 #[cfg(feature = "timer")]
 use tokio_timer::{
-    debounce::{Debounce, DebounceBuilder, Edge},
     throttle::Throttle,
-    timeout::Timeout,
+    Timeout,
 };
 
 use futures::Stream;
@@ -25,63 +24,6 @@ use std::time::Duration;
 ///
 /// [`timeout`]: #method.timeout
 pub trait StreamExt: Stream {
-    /// Debounce the stream on the trailing edge using the given duration.
-    ///
-    /// Errors will pass through without being debounced. Debouncing will
-    /// happen on the trailing edge. This means all items (except the last
-    /// one) will be discarded until the delay has elapsed without an item
-    /// being passed through. The last item that was passed through will
-    /// be returned.
-    ///
-    /// Care must be taken that this stream returns `Async::NotReady` at some point,
-    /// otherwise the debouncing implementation will overflow the stack during
-    /// `.poll()` (i. e. don't use this directly on `stream::repeat`).
-    ///
-    /// See also [`debounce_builder`], which allows more configuration over how the
-    /// debouncing is done.
-    ///
-    /// [`debounce_builder`]: #method.debounce_builder
-    fn debounce(self, dur: Duration) -> Debounce<Self>
-    where Self: Sized
-    {
-        self.debounce_builder()
-            .duration(dur)
-            .edge(Edge::Trailing)
-            .build()
-    }
-
-    /// Create a builder that builds a debounced version of this stream.
-    ///
-    /// The returned builder can be used to configure the debouncing process.
-    ///
-    /// Care must be taken that this stream returns `Async::NotReady` at some point,
-    /// otherwise the debouncing implementation will overflow the stack during
-    /// `.poll()` (i. e. don't use this directly on `stream::repeat`).
-    fn debounce_builder(self) -> DebounceBuilder<Self>
-    where Self: Sized
-    {
-        DebounceBuilder::from_stream(self)
-    }
-
-    /// Sample the stream at the given `interval`.
-    ///
-    /// Sampling works similar to debouncing in that frequent values will be
-    /// ignored. Sampling, however, ensures that an item is passed through at
-    /// least after every `interval`. Debounce, on the other hand, would not
-    /// pass items through until there has been enough "silence".
-    ///
-    /// Care must be taken that this stream returns `Async::NotReady` at some point,
-    /// otherwise the sampling implementation will overflow the stack during
-    /// `.poll()` (i. e. don't use this directly on `stream::repeat`).
-    fn sample(self, interval: Duration) -> Debounce<Self>
-    where Self: Sized
-    {
-        self.debounce_builder()
-            .max_wait(interval)
-            .edge(Edge::Leading)
-            .build()
-    }
-
     /// Throttle down the stream by enforcing a fixed delay between items.
     ///
     /// Errors are also delayed.