Added lines, refactored expand_tabs.
Added lines, refactored expand_tabs.

Removed dependency on penlight's stringx.lines, which
has a bug.

simoncozens/lunamark,simoncozens/lunamark,tst2005/lunamark,jgm/lunamark,jgm/lunamark,jgm/lunamark,simoncozens/lunamark,tst2005/lunamark,tst2005/lunamark