Refactor test

 - Changed draw methods bounds testing to its own test

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

@@ -97,6 +97,11 @@ public class DotsAndBoxesGridTest {
         case1.drawVertical(0, 0, 0);
       }
     );
+  }
+
+  @Test
+  public void drawMethodsStayWithinBounds() {
+    DotsAndBoxesGrid case1 = new DotsAndBoxesGrid(width, height, 2);
 
     /*
      * Drawn lines are within game board bounds