Classify: Toggle buttons: Don't use a custom style.

Because, even when setting textColor, textSize and textStyle to @null,
we still don't get quite the same appearance as with textAppearance on
the Button itself. Incidentally, for some reason using
android:textStyle="@null"
fails style validation though it works for textColor and textSize.
I assume that the appearance is more correct when using the
textAppearance directly on the Button in the layout.
Classify: Give the buttons a slight background color.

And make the margin between buttons as small as possible (1dp) and
add some bottom padding inside the buttons.
This makes the separation between the buttons more obvious,
as discussed here:
https://plus.google.com/100123542880051296706/posts/WcjVd8zKT7e
though I personally prefer the buttons without backgrounds.