Drop rustc-serialize dependency

[dtolnay]

It has been deprecated: announcement.

[cardoe]

I'd honestly love to. I've stopped using it and switched to Serde for most of my projects already. The reason for this is that I use Cargo to parse the args and the latest Cargo version, 0.17 requires struct that defines the options to derive RustcDecodable.

[cardoe]

Here's the current error when I attempt to use Serde.

let result = cargo::call_main_without_stdin(real_main, &config, USAGE, &args, false);
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `rustc_serialize::serialize::Decodable` is not implemented for `Options`

[dtolnay]

Cool, I filed rust-lang/cargo#3944 to track this on Cargo's end.

[cardoe]

Thanks. I might drop using that entry point and switch to clap to parse the args and then I can drop rustc-serialize.