Handle the new read-manifest --manifest-path behaviour.
Handle the new read-manifest --manifest-path behaviour.

cc https://github.com/rust-lang/cargo/pull/1955

Closes #18.

badboy/travis-cargo,badboy/travis-cargo,erickt/travis-cargo,kbknapp/travis-cargo,huonw/travis-cargo,erickt/travis-cargo,kbknapp/travis-cargo,huonw/travis-cargo,erickt/travis-cargo,badboy/travis-cargo,kbknapp/travis-cargo,huonw/travis-cargo