Rename Client::request -> send_request (#98)

All other fns have a send prefix.

examples/akamai.rs

@@ -75,7 +75,7 @@ pub fn main() {
                     .body(())
                     .unwrap();
 
-                let stream = h2.request(request, true).unwrap();
+                let stream = h2.send_request(request, true).unwrap();
 
                 let stream = stream.and_then(|response| {
                     let (_, body) = response.into_parts();