fix(readme): add deprecation notice

Author: pvdlg

README.md

@@ -6,7 +6,11 @@ Run a deployment script only once in the [Travis](https://travis-ci.org/) test m
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-**Note**: Travis supports [Build Stages](https://docs.travis-ci.com/user/build-stages) as a beta feature. We recommend to use Build Stages instead of `travis-deploy-once` if possible. It’s a clearer and more flexible way to orchestrate jobs within a build.
+## :warning: Deprecation Notice :warning:
+
+**This library is deprecated and will not be maintained. We recommend to use [Build Stages](https://docs.travis-ci.com/user/build-stages) instead. It’s a clearer and more flexible way to orchestrate jobs within a build.**
+
+## Overview
 
 For Travis builds running multiple jobs (to test with multiple [Node versions](https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#Specifying-Node.js-versions) and/or [OSs](https://docs.travis-ci.com/user/multi-os)), `travis-deploy-once` run some code only once, after all other jobs have completed successfully.