[META] Future runner capabilities

This issue holds a discussion about future features and capabilities to add to apps that run on the Deis platform. Discussions herein may relate to `deis/workflow`, `deis/slugbuilder`, `deis/slugrunner` and others.

Whiteboard discussion notes from 1/21/2016:


This is a cross-project whiteboard discussion involving deis/workflow, deis/slugbuilder, and deis/slugrunner. Start by reviewing the discussion notes and the linked project context; no files, tests, entry point, or acceptance criteria are named, so the issue does not define a concrete done condition.

Written by the indexing model from the issue text.