Fix "method_lines" issue in src/leaderBoard/LeaderBoard.js

[fernandosouza]

Function renderWinnerMessage_ has 26 lines of code (exceeds 25 allowed). Consider refactoring.

https://codeclimate.com/github/fernandosouza/react-tic-tac-toe/src/leaderBoard/LeaderBoard.js#issue_5db85bfd23597d0001000037