Added Ord and Hash as derived traits for tokio::time::Instant (#2239)
Added Ord and Hash as derived traits for tokio::time::Instant (#2239)

The added derived traits mirror the traits of std::time::Instant. As
tokio::time::Instant is just a wrapper around std::time::Instant, it
should also derive all the traits std::time::Instant derives.
tokio-rs/tokio,tokio-rs/tokio