Support for Cloud Foundry Auth method

[devgig]

HashiCorp Vault has recently rolled out a Cloud Foundry Auth method https://www.vaultproject.io/docs/auth/cf/. This is something all the cloud foundry users can benefit from. I have working code and an example. Please let me know if you want me to add this. I can do a PR and include the additional feature.

[Marusyk]

Hi @devgig,

Thanks for your interest in this project.
I think it's a great idea. But the project owner did not respond for a long time. We have quite an active fork, announced in #118.

So if you're motivated that would be welcome!
https://github.com/VaultSharp/VaultSharp