touchList-segment-header style update

Before:
![before](http://i.imgur.com/E6dJ62z.png)

After:
![after](http://i.imgur.com/FZdLG66.png)

_Note_: The original style aimed for a $H_touchTargetMinimum height, which seems preferable to the design's not-quite-full-height, which is why the 'After' style has shorter headings than the design. @mperrotti, feel free to request a different height treatment.

Design:
![design](http://i.imgur.com/ZY6eSgV.png)