Refactor gzip and brotli bools into an Accepts struct

src/async_impl/mod.rs

@@ -1,9 +1,11 @@
 pub use self::body::Body;
 pub use self::client::{Client, ClientBuilder};
-pub(crate) use self::decoder::Decoder;
 pub use self::request::{Request, RequestBuilder};
 pub use self::response::{Response, ResponseBuilderExt};
 
+#[cfg(feature = "blocking")]
+pub(crate) use self::decoder::Decoder;
+
 pub mod body;
 pub mod client;
 pub mod decoder;