feat(lib): switch to non-blocking (asynchronous) IO

BREAKING CHANGE: This breaks a lot of the Client and Server APIs.
  Check the documentation for how Handlers can be used for asynchronous
  events.

src/uri.rs

@@ -50,6 +50,12 @@ pub enum RequestUri {
     Star,
 }
 
+impl Default for RequestUri {
+    fn default() -> RequestUri {
+        RequestUri::Star
+    }
+}
+
 impl FromStr for RequestUri {
     type Err = Error;
 
@@ -67,7 +73,7 @@ impl FromStr for RequestUri {
             let mut temp = "http://".to_owned();
             temp.push_str(s);
             try!(Url::parse(&temp[..]));
-            todo!("compare vs u.authority()");
+            //TODO: compare vs u.authority()?
             Ok(RequestUri::Authority(s.to_owned()))
         }
     }