Publishable to Crates.io

[dmfutcher]

We want to start publishing spotify-connect-scrobbler to Crates.io. Currently, this crate is not publishable due to some unpublished dependencies. I'm working with their author to have them published. Tracking list:

• rust-protobuf-macros
• librespot-core
• librespot-metadata
• librespot-protocol

[dmfutcher]

There are some packages in Cargo.toml that point to git repos rather than packages on Crates.io: hyper, rust-mdns, rust-tremor, rust-protobuf-macros, rust-crypto.

• hyper should be able to point at the latest version on Crates.io, I've got it building and it seems fine
• rust-tremor can be removed with associated code changes (it's playback related)
• rust-mdns relates to MDNS discovery. It's not published on Crates.io, may be able to replace with a different library, or remove the code altogether. It's not entirely clear what it does at this point.
• rust-crypto points to a forked avx2 branch, which removes AVX requirement from the published version. I'm happy to require AVX2 at the moment. Could work with upstream rust-crypto to get the AVX branch merged behind a feature flag but the project seems pretty quiet.
• rust-protobuf-macros is another plietar project only published on Git. Looks pretty painful to remove from the code, but plietar has resigned control of librespot so it may be difficult to get this published on Crates.

[dmfutcher]

Since syncing with the latest librespot master (issue #5), this situation has changed a bit. The majority of the old librespot code is split into -core, -audio, -protocol, and -metadata sub-crates. I'm working with plietar to get the ones we need (all but -audio) published to Crates.io with all required dependencies, some of which we also need directly in s-c-s (rust-protobuf-macros).