Add deprecation notice

[Birdrock]

WHAT is this change about?

Add deprecation notice to project.

Tag your pair, your PM, and/or team

@PureMunky

Things to remember

• Make sure this PR is based off the develop branch
• Include any links to related PRs, issues, stories, slack discussions, etc... that will help establish context.
• Is there anything else of note that the reviewers should know about this change?
• Our CI uses concourse task files from HEAD of the develop branch. If your PR includes/requires CI changes, please ping the RelInt interrupt and they'll help apply the CI changes for you.
• Checkout the contributing guidelines

[cf-gitbot]

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

https://www.pivotaltracker.com/story/show/182811820

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