update example error handling

- Add error-chain dev dependency
- Add error handling using `?` instead of `unwrap`

examples/simple.rs

@@ -1,17 +1,31 @@
+//! `cargo run --example simple`
 extern crate reqwest;
 extern crate env_logger;
+#[macro_use] extern crate error_chain;
 
-fn main() {
-    env_logger::init().unwrap();
+error_chain! {
+    foreign_links {
+        ReqError(reqwest::Error);
+        IoError(std::io::Error);
+    }
+}
+
+fn run() -> Result<()> {
+    env_logger::init()
+        .expect("Failed to initialize logger");
 
     println!("GET https://www.rust-lang.org");
 
-    let mut res = reqwest::get("https://www.rust-lang.org").unwrap();
+    let mut res = reqwest::get("https://www.rust-lang.org")?;
 
     println!("Status: {}", res.status());
     println!("Headers:\n{}", res.headers());
 
-    ::std::io::copy(&mut res, &mut ::std::io::stdout()).unwrap();
+    // copy the response body directly to stdout
+    let _ = std::io::copy(&mut res, &mut std::io::stdout())?;
 
     println!("\n\nDone.");
+    Ok(())
 }
+
+quick_main!(run);