Review deployment tools as future application

This is important to review possible applications for dag library which might highlight important requirements.
1. https://github.com/capistrano/capistrano
2. https://github.com/ansistrano/deploy
3. https://github.com/fabric/fabric
4. https://github.com/gulpjs/gulp

The issue names no files, tests, or entry points. Begin by reviewing the four linked deployment tools—Capistrano, Ansistrano Deploy, Fabric, and Gulp—and identify the DAG library requirements or applications they reveal; done is a decided requirements or applications list.

Written by the indexing model from the issue text.