Proof of concept for building without errors due to unused serde_derive macro.
@@ -56,6 +56,7 @@ extern crate ring;
extern crate rusoto_credential;
extern crate rustc_serialize;
extern crate serde;
+#[cfg(any(feature = "ecs", feature = "all", feature = "packagea", feature = "packageb"))]
#[macro_use]
extern crate serde_derive;
extern crate serde_json;
