Metadata crate means we can't publish Racer

[nrc]

cargo publish only publishes a single crate, so the crates referred to by path aren't included. In particular metadata is not part of the published tarball. That means the we fail the pre-publish check, and if we ignore that, the published version would not build.

Solutions are: publish anyway and document that it cannot be used with the metadata feature (note that it is used by default), publish the metadata crate and refer to it by version not path, or moving the contents of the crate into Racer proper.