Refactor to remove instance_eval

When you have a hammer...

lib/squib/graphics/shapes.rb

@@ -84,7 +84,6 @@ module Squib
       x, y, n = poly.x, poly.y, poly.n
       inner_radius, outer_radius = poly.inner_radius, poly.outer_radius
       use_cairo do |cc|
-        poly.instance_eval do
         cc.rotate_about(x, y, trans.angle)
         cc.move_to(x + outer_radius, y) #i = 0, so cos(0)=1 and sin(0)=0
         theta = Math::PI / n.to_f # i.e. (2*pi) / (2*n)
@@ -93,7 +92,6 @@ module Squib
             cc.line_to(x + radius * Math::cos(i * theta),
                        y + radius * Math::sin(i * theta))
         end
-        end
         cc.close_path
         cc.fill_n_stroke(draw)
       end