add issue-15-6-callmewhy.md
Rename issue-15-6-callmewhy.md to issue-16-6-callmewhy.md

change file name
Rename issue-16-6-callmewhy.md to issue-16-4-callmewhy.md

rename
Reviewed
Merge pull request #259 from objccn/new/issue-16-4-callmewhy

New/issue 16 4 callmewhy