support custom root CAs

[drnic]

Currently uaa target only supports --skip-ssl-validation to ignore custom root certificates. Could we add support for a --ca-cert flag too please?

Related to cloudfoundry/go-uaa#5

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/158932805

The labels on this github issue will be updated when the story is started.

[joefitzgerald]

This seems worth doing. I will think through how we resolve this in the client in cloudfoundry/go-uaa#5.