Fix 2px clipping of date in table

Date width was set to 76px but the width constraint was set to 74px.
Increase date/time font sizes

* Increase date font size to 14pt
* Increase time font size to 11pt
Change table cell background color to web gray

The contrast between the date/time text and the dark-ish gray of the
table cell background isn't so great, but changing the background to
the lighter gray used on the web makes things a little easier to read.
Merge pull request #245 from samford/master

Fix 2px date clipping and make date/time headers a little more readible