Adding option for adding a CA

[noahwaldner]

For use in a corperate environment the option for a custom CA should be added.

At the Moment the Error "UNABLE_TO_VERIFY_LEAF_SIGNATURE" appears.

[ronanquillevere]

We should be able to configure superagent behavior as this is a dependency of the lib, so that we can use .ca(), .cert() : https://visionmedia.github.io/superagent/#tls-options

[compwright]

@noahwaldner @ronanquillevere I've released v2.1.0, which uses axios under the hood. You can pass in extra configuration, or a pre-configured axios instance via the client parameter.

See axios configs here: https://github.com/axios/axios#request-config

In particular note httpsAgent which you can configure like this: https://github.com/axios/axios#request-config

[ronanquillevere]

Great thank you ! @compwright