Vendor dependencies

Let's see how I like this workflow.

vendor/tokio-stream/tests/stream_pending.rs

@@ -0,0 +1,14 @@
+use tokio_stream::{self as stream, Stream, StreamExt};
+use tokio_test::{assert_pending, task};
+
+#[tokio::test]
+async fn basic_usage() {
+    let mut stream = stream::pending::<i32>();
+
+    for _ in 0..2 {
+        assert_eq!(stream.size_hint(), (0, None));
+
+        let mut next = task::spawn(async { stream.next().await });
+        assert_pending!(next.poll());
+    }
+}