Update tests.py
Update tests.py

improve test data "['a   B\n','b   B\n','c   I\n','d   B\n','e   I\n','f   I\n', \
        '\n','g   B\n','h   I\n','i   B\n']" 
in def test_slice_lines(self):
photonxp/word_slicer_demo