Config option to change SSL validation needed

[LindsayHill]

As a user, I would like to have the option to specify verify: False, or provide a path to an alternative CA bundle.

This will allow me to use this pack with self-hosted Jira systems that have certificates signed by internal CAs, or self-signed certificates.

The jira library supports it, so it should just be a pack-level change.

Note that the requests library when used in a Python virtualenv uses its own cacert.pem file, not the system CA store. So the usual process, of adding the CA certificate to /etc/ssl/certs won't work.

[punkrokk]

This is a very common use case. +1