Needed to set squibcolor prior to translating the coordinate system so that gradients are relative to the card (as is documented). This also means stroking is done AFTER drawing the text, which looks better anyway.
Fill color is still the same with 'color' (i.e. can be overridden by markup still), but now there's a stroke_width and a stroke_color option that, when stroke_width > 0, will draw an outline below the text. Since this isn't a Pango feature, we can't do markup for outlines. (Maybe make that a feature request to Pango if you want it.)
Implements #51
Andy Meneely