Revamp README.md [skip-ci]

- restructure README.md to be valid markdown syntax
- add TODO text to README sections that need work
- clearly differentiate mob programming from the other mob
- add link to mobprogramming.org in new "Additional Resources" section
- place "Instructions For Use" section below "Features" section
- capitalize "Instructions For Use"
Merge pull request #12 from dleve123/readme-cleanup

README Cleanup