chore(features): remove feature gate 'alloc'

src/client/request.rs

@@ -176,7 +176,6 @@ impl Write for Request<Streaming> {
 
 #[cfg(test)]
 mod tests {
-    use std::boxed::BoxAny;
     use std::str::from_utf8;
     use url::Url;
     use method::Method::{Get, Head};

src/client/response.rs

@@ -103,7 +103,6 @@ impl Read for Response {
 #[cfg(test)]
 mod tests {
     use std::borrow::Cow::Borrowed;
-    use std::boxed::BoxAny;
     use std::io::{self, Read};
     use std::marker::PhantomData;