code: function(inlines) {
    if (this.peek() == '\n') {
      this.pos++;
      var last = inlines[inlines.length - 1];
      if (last && last.t == 'Str' && last.c.slice(-2) == '  ') {
        last.c = last.c.replace(/ *$/,'');
        inlines.push({ t: 'Hardbreak' });
      } else {
        if (last && last.t == 'Str' && last.c.slice(-1) == ' ') {
          last.c = last.c.slice(0, -1);
        }
        inlines.push({ t: 'Softbreak' });
      }
      return 1;
    } else {
      return 0;
    }
  }
docs: Parse a newline.  If it was preceded by two spaces, return a hard line break; otherwise a soft line break.