Apply deadline across redirects. (#313)

Previously, each redirect could take timeout time, so a series of slow
redirects could run for longer than expected, or indefinitely.

src/request.rs

@@ -1,5 +1,5 @@
-use std::fmt;
 use std::io::Read;
+use std::{fmt, time};
 
 use url::{form_urlencoded, Url};
 
@@ -116,8 +116,23 @@ impl Request {
         for (name, value) in self.query_params.clone() {
             url.query_pairs_mut().append_pair(&name, &value);
         }
+        let deadline = match self.agent.config.timeout {
+            None => None,
+            Some(timeout) => {
+                let now = time::Instant::now();
+                Some(now.checked_add(timeout).unwrap())
+            }
+        };
+
         let reader = payload.into_read();
-        let unit = Unit::new(&self.agent, &self.method, &url, &self.headers, &reader);
+        let unit = Unit::new(
+            &self.agent,
+            &self.method,
+            &url,
+            &self.headers,
+            &reader,
+            deadline,
+        );
         let response = unit::connect(unit, true, reader).map_err(|e| e.url(url.clone()))?;
 
         if response.status() >= 400 {