partially fixes #9 (GH): implement / and n motions
start implementing , and ; motions
fixes #28 (GH): dd in last line must delete the whole line too if line is not empty
improve n
fix #16 (GH): * must search whole word only
fixes #26 (GH): X at BOL should not delete newline; improve x
fixes #27 (GH): X in visual mode should behave linewise