* add back train method but mark as deprecated * fix scalastyle error * change class to object in examples * fix compilation error * bump spark version to 2.1 * preserve num_class issues * fix failed test cases * rivising * add multi class test
* add back train method but mark as deprecated * fix scalastyle error * change class to object in examples * fix compilation error * bump spark version to 2.1 * preserve num_class issues * fix failed test cases * rivising * add multi class test