Vendor dependencies

Let's see how I like this workflow.

vendor/flate2/tests/early-flush.rs

@@ -0,0 +1,20 @@
+extern crate flate2;
+
+use std::io::{Read, Write};
+
+use flate2::read::GzDecoder;
+use flate2::write::GzEncoder;
+
+#[test]
+fn smoke() {
+    let mut w = GzEncoder::new(Vec::new(), flate2::Compression::default());
+    w.flush().unwrap();
+    w.write_all(b"hello").unwrap();
+
+    let bytes = w.finish().unwrap();
+
+    let mut r = GzDecoder::new(&bytes[..]);
+    let mut s = String::new();
+    r.read_to_string(&mut s).unwrap();
+    assert_eq!(s, "hello");
+}