Using a platform-specific fix for zero-width letters on embedding icons

Contributes to #30 and our zero-width letter woes.

spec/graphics/graphics_text_spec.rb

@@ -40,9 +40,7 @@ describe Squib::Card, '#text' do
       expect(layout ).to receive(:height).once.and_return(25)
       expect(layout ).to receive(:extents).thrice.and_return([nil,extent])
       expect(context).to receive(:update_pango_layout).once
-      expect(context).to receive(:matrix).and_return(Cairo::Matrix.new(1, 0, 0, 1, 0, 0)).once
       expect(context).to receive(:show_pango_layout).once
-      expect(context).to receive(:matrix=).once
       expect(context).to receive(:restore).once
 
       card = Squib::Card.new(deck, 100, 150)