Update the client API to statically track headers and move constructors

The client Request now uses the same system as a server Response to track
the write status of headers, and the API has been updated accordingly.

Additionally, the Request constructors have been moved onto the Request object
instead of being top-level hyper functions, as this better namespaces the
client and Server.

src/client/mod.rs

@@ -1,38 +1,7 @@
 //! HTTP Client
-use url::Url;
-
-use method::{Get, Head, Post, Delete, Method};
-
 pub use self::request::Request;
 pub use self::response::Response;
-use {HttpResult};
 
 pub mod request;
 pub mod response;
 
-
-/// Create a GET client request.
-pub fn get(url: Url) -> HttpResult<Request> {
-    request(Get, url)
-}
-
-/// Create a HEAD client request.
-pub fn head(url: Url) -> HttpResult<Request> {
-    request(Head, url)
-}
-
-/// Create a POST client request.
-pub fn post(url: Url) -> HttpResult<Request> {
-    // TODO: should this accept a Body parameter? or just let user `write` to the request?
-    request(Post, url)
-}
-
-/// Create a DELETE client request.
-pub fn delete(url: Url) -> HttpResult<Request> {
-    request(Delete, url)
-}
-
-/// Create a client request.
-pub fn request(method: Method, url: Url) -> HttpResult<Request> {
-    Request::new(method, url)
-}