Adds testability report for 4th sprint.
Adds installability report for 4th sprint.
Merge branch 'master' of https://github.com/SEP007/resources

* 'master' of https://github.com/SEP007/resources:
  Update 1st-measurement-report.md
  Rename  sprint-4.md to sprint-4.md
  Update README.md
  Create report deadlines.md
  Update sprint-retrospective.md
  Updated suitability metrics
  Update upgrade-guide.md