Add a `--check-certificate` command line option

[kylewillmon]

If the user sets ignore_certs in their config file, there is currently no way to force the CLI to check certificates without modifying that file.

[cd-work]

While this makes sense in theory, I wonder how relevant it would be in practice? If you send so much stuff without certificates that you even set it in your config file, do you really have the need to manually send stuff with certificates in one-off requests?