Traces to Chrome's trace_event format

Example

Cargo.toml:

rs_tracing = { version = "1.0", features = ["rs_tracing"] }

main.rs:

fn main() {
    open_trace_file!(".").unwrap();
    {
        trace_scoped!("complete","custom data":"main");
        trace_expr!("trace_expr", println!("trace_expr"));
        trace_begin!("duration");
        println!("trace_duration");
        trace_end!("duration");
    }
    close_trace_file!();
}

also possible to add custom data to all the macros formated like the serde_json::json! macro e.g.

trace_scoped!("complete","custom":230,"more":"data");