I've replaced rustc_serialize (which is not seeing much, if any, new development) with serde and serde_json. Tests are passing on my machine, the change was actually pretty painless and quick.
That said, this is still probably a breaking change (I haven't looked at how much of rustc_serialize, if any, was exported through this library) and I haven't changed the docs yet to reflect the change.
I've replaced rustc_serialize (which is not seeing much, if any, new development) with serde and serde_json. Tests are passing on my machine, the change was actually pretty painless and quick.
That said, this is still probably a breaking change (I haven't looked at how much of rustc_serialize, if any, was exported through this library) and I haven't changed the docs yet to reflect the change.