Add beta and v1.x roadmap
Let's add a roadmap to the root of the project to layout:
- the enhancements and fixes we'll add to the v1.0.0-beta
- the enhancement freeze date for beta
- the testing phase date range for beta
- the release date for beta
- the documentation enhancements for v1.0.0
- the testing phase date range for v1.0.0
- the release date for v1.0.0
- the proposed scope of the next release