[2.0.0] - 2022-10-07 changed: * BREAKING: changed `Guard::new` to return `libsw::Result<Guard>` * BREAKING: changed `Error` * replaced all variants with `SwStart`, `SwStop`, `SwGuard`, and `GuardNew` * marked `non_exhaustive` * added `Error::expects_running` * added `Error::expects_stopped` * changed `Display` impl * changed `Stopwatch::guard` and `Stopwatch::guard_at` to return `Error::SwGuard` * shortened impl of `Stopwatch::start_at` and `Stopwatch::stop_at` * replaced unreachable unwrap in `Stopwatch::guard_at` with debug assertion * re-licensed under `MIT OR Apache-2.0`