Remove cli plugin from diego-ssh

[sykesm]

The cli team has integrated the authentication and interactive shell functions into the core.

[cfdreddbot]

Hey sykesm!

Thanks for submitting this pull request! I'm here to inform the recipients of the pull request that you've already signed the CLA.

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this. You can view the current status of your issue at: https://www.pivotaltracker.com/story/show/110773500.

[emalm]

Thanks for the cleanup, @sykesm! We'll release version 0.2.2 of the plugin to incorporate the changes from #13, and then plan to merge this and cloudfoundry/diego-release#120.

Thanks again,
Eric