cargo check emits warnings about `--crate-type=metadata` being deprecated

[japaric]

As of nightly-2017-01-04:

$ cargo new --lib foo && cd $_

$ cargo check
   Compiling foo v0.1.0 (file:///home/japaric/tmp/foo)
warning: --crate-type=metadata is deprecated, prefer --emit=metadata

    Finished debug [unoptimized + debuginfo] target(s) in 0.9 secs

$ rustc -V
rustc 1.16.0-nightly (468227129 2017-01-03)

$ cargo -V
cargo 0.17.0-nightly (71e996e 2017-01-02)

cc @alexcrichton @nrc

[nrc]

This should be fixed by #3468 (which is waiting on a nightly to work in order to pass tests, plus some other tests getting tweaked).

[alexcrichton]

Ah yeah this'll be fixed with a new nightly, so closing.