Add some useful #![deny(...)] lints:
- missing_docs to disallow undocumented public items;
- missing_debug_implementations for public types;
- no unsafe code or unstable features.
The ListenBrainz struct is a more ergonomic client
than raw::Client. It supports authentication using
a ListenBrainz token. Currently, it allows submitting
"listened" and "now playing" requests to the API
in a more convenient way than manually creating all
request data.