Remove the unused EncodingDecoder

The project "encoding" appears to be unmaintained, and hasn't received
an update since 2017. Unfortunately the "encoding" artifacts on
crates.io do not contain the licenses for the project, which adds
difficulty in auditing dependencies.

Since "tiny-http" doesn't actually use the EncodingDecoder, this patch
removes it and it's dependency on "encoding" in order to avoid
complications resolving the "tiny-http" dependency story.

Instead, I would suggest investigating migrating over to
https://docs.rs/encoding_rs/0.8.13/encoding_rs/, which appears to be
actively maintained by Mozilla.

If this patch is accepted, would it be possible to get a release as
well?

Cargo.toml

@@ -16,7 +16,6 @@ ssl = ["openssl"]
 [dependencies]
 ascii = "0.8"
 chunked_transfer = "0.3"
-encoding = "0.2"
 openssl = { version = "0.10", optional = true }
 url = "1.7"
 chrono = "0.4"

src/lib.rs

@@ -112,7 +112,6 @@ extern crate log;
 
 extern crate ascii;
 extern crate chunked_transfer;
-extern crate encoding;
 extern crate url;
 extern crate chrono;
 
@@ -142,7 +141,6 @@ mod common;
 mod request;
 mod response;
 
-#[allow(dead_code)]     // TODO: remove when everything is implemented
 mod util;
 
 /// The main class of this library.

src/util/mod.rs

@@ -13,7 +13,6 @@
 // limitations under the License.
 
 pub use self::custom_stream::CustomStream;
-pub use self::encoding_decoder::EncodingDecoder;
 pub use self::equal_reader::EqualReader;
 pub use self::messages_queue::MessagesQueue;
 pub use self::refined_tcp_stream::RefinedTcpStream;
@@ -24,7 +23,6 @@ pub use self::task_pool::TaskPool;
 use std::str::FromStr;
 
 mod custom_stream;
-mod encoding_decoder;
 mod equal_reader;
 mod messages_queue;
 mod refined_tcp_stream;