If set to true, httpstat will only output metrics in json format, this is useful if you want to parse the data instead of reading it. 
1.2.1
- Add `HTTPSTAT_SHOW_IP` env to control IP display feature - Say TLS instead of SSL
1.2.0
- Add HTTPSTAT_CURL_BIN env var to support customize curl bin path - Add HTTPSTAT_SAVE_BODY env var to control body temp file storage - Various display & code enhancements
1.1.3
- disable color when stdout is not a tty
1.1.2
- add env header for execution - fix LC_ALL numeric problem in issue 1
1.1.0
- Use `Transport.ForceAttemptHTTP2 ` to enable HTTP/2 - Added -4 and -6 flags