Treegrid Example: Some focus rectangles overlap neighboring cells

[mcking65]

Per comments from @annabbott in issue #132, the treegrid example has bugs in focus rectangle sizing:

Focus rectangle for Summary cell overlaps into Email cell in rows 3 through 8. Focus rectangle for Subject cell overlaps into Summary cell in rows 7 and 8. Email underline exceeds right edge of visible grid in rows 5 and 7.