Merge pull request #593 from morrme/mine-remove-final

minesweeper: remove "final" from class declaration

exercises/minesweeper/src/test/java/MinesweeperBoardTest.java

 
 import static org.junit.Assert.assertEquals;
 
-public final class MinesweeperBoardTest {
+public class MinesweeperBoardTest {
 
     /*
      * See https://github.com/junit-team/junit4/wiki/Rules for information on JUnit Rules in general and