Migrate serde dependency to use derive feature

This is in line with best practices recommended
by serde[1]. This will also resolve downstream
crates depending on shiplift who enable the
serde derive feature, due to Cargos unification
of features for each crate[2].

[1]: serde-rs/serde#1441
[2]: rust-lang/cargo#4361 (comment)

Cargo.toml

@@ -34,8 +34,7 @@ tokio = "0.1.15"
 tokio-codec = "0.1.1"
 tokio-io = "0.1.11"
 url = "1.7.2"
-serde = "1.0.87"
-serde_derive = "1.0.87"
+serde = { version = "1.0.87", features = ["derive"] }
 serde_json = "1.0.38"
 
 [dev-dependencies]

src/builder.rs

@@ -2,7 +2,6 @@
 
 use crate::{errors::Error, Result};
 use serde::Serialize;
-use serde_derive::Serialize;
 use serde_json::{self, json, map::Map, Value};
 use std::{
     cmp::Eq,

src/rep.rs

@@ -1,6 +1,6 @@
 //! Rust representations of docker json structures
 
-use serde_derive::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
 #[derive(Clone, Debug, Serialize, Deserialize)]

src/transport.rs

@@ -17,7 +17,7 @@ use hyperlocal::UnixConnector;
 use hyperlocal::Uri as DomainUri;
 use log::debug;
 use mime::Mime;
-use serde_derive::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize};
 use serde_json;
 use std::fmt;
 use tokio_io::{AsyncRead, AsyncWrite};