Merge pull request #880 from mortenaa/MatrixAddStubs

Added stubs to Matrix #547

exercises/matrix/src/main/java/Matrix.java

+
+class Matrix {
+
+    Matrix(String matrixAsString) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    int[] getRow(int rowNumber) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    int[] getColumn(int columnNumber) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    int getRowsCount() {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    int getColumnsCount() {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+}