Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/io_lines.rs

@@ -0,0 +1,19 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use tokio::io::AsyncBufReadExt;
+use tokio_test::assert_ok;
+
+#[tokio::test]
+async fn lines_inherent() {
+    let rd: &[u8] = b"hello\r\nworld\n\n";
+    let mut st = rd.lines();
+
+    let b = assert_ok!(st.next_line().await).unwrap();
+    assert_eq!(b, "hello");
+    let b = assert_ok!(st.next_line().await).unwrap();
+    assert_eq!(b, "world");
+    let b = assert_ok!(st.next_line().await).unwrap();
+    assert_eq!(b, "");
+    assert!(assert_ok!(st.next_line().await).is_none());
+}