Fix Response doc-tests to actually use Response

Some of them were testing the methods from `Request` instead.

src/response.rs

@@ -83,9 +83,9 @@ impl Response {
  /// ```
  /// # fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
  /// #
- /// use http_types::{Url, Method, Request};
+ /// use http_types::{Url, Method, Response, StatusCode};
  ///
- /// let mut req = Request::new(Method::Get, Url::parse("https://example.com")?);
+ /// let mut req = Response::new(StatusCode::Ok);
  /// req.insert_header("Content-Type", "text/plain")?;
  /// #
  /// # Ok(()) }
@@ -145,7 +145,7 @@ impl Response {
  }
  }
 
- /// Replace the request body with a new body, returning the old body.
+ /// Replace the response body with a new body, returning the old body.
  ///
  /// # Examples
  ///
@@ -154,9 +154,9 @@ impl Response {
  /// # fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
  /// # async_std::task::block_on(async {
  /// #
- /// use http_types::{Body, Url, Method, Request};
+ /// use http_types::{Body, Url, Method, Response, StatusCode};
  ///
- /// let mut req = Request::new(Method::Get, Url::parse("https://example.com")?);
+ /// let mut req = Response::new(StatusCode::Ok);
  /// req.set_body("Hello, Nori!");
  ///
  /// let mut body: Body = req.replace_body("Hello, Chashu");
@@ -181,9 +181,9 @@ impl Response {
  /// # fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
  /// # async_std::task::block_on(async {
  /// #
- /// use http_types::{Body, Url, Method, Request};
+ /// use http_types::{Body, Url, Method, Response, StatusCode};
  ///
- /// let mut req = Request::new(Method::Get, Url::parse("https://example.com")?);
+ /// let mut req = Response::new(StatusCode::Ok);
  /// req.set_body("Hello, Nori!");
  ///
  /// let mut body = "Hello, Chashu!".into();
@@ -199,7 +199,7 @@ impl Response {
  mem::swap(&mut self.body, body);
  }
 
- /// Take the request body, replacing it with an empty body.
+ /// Take the response body, replacing it with an empty body.
  ///
  /// # Examples
  ///
@@ -208,9 +208,9 @@ impl Response {
  /// # fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
  /// # async_std::task::block_on(async {
  /// #
- /// use http_types::{Body, Url, Method, Request};
+ /// use http_types::{Body, Url, Method, Response, StatusCode};
  ///
- /// let mut req = Request::new(Method::Get, Url::parse("https://example.com")?);
+ /// let mut req = Response::new(StatusCode::Ok);
  /// req.set_body("Hello, Nori!");
  /// let mut body: Body = req.take_body();
  ///