Refactor to remove instance_eval

When you have a hammer...

lib/squib/graphics/shapes.rb

@@ -84,15 +84,13 @@ 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)
-          0.upto(2 * n) do |i|
-              radius = i.even? ? outer_radius : inner_radius
-              cc.line_to(x + radius * Math::cos(i * theta),
-                         y + radius * Math::sin(i * theta))
-          end
+        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)
+        0.upto(2 * n) do |i|
+            radius = i.even? ? outer_radius : inner_radius
+            cc.line_to(x + radius * Math::cos(i * theta),
+                       y + radius * Math::sin(i * theta))
         end
         cc.close_path
         cc.fill_n_stroke(draw)