Added notice about segfault in Gosu::Window usage

lib/main_window.rb

@@ -3,7 +3,6 @@
 require 'ball'
 
 class MainWindow < Gosu::Window
-
   TITLE = "Bouncing Ball"
 
   def initialize

spec/main_window_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+# there is a segfault bug that is caused when you try to re-use a Gosu::MainWindow
+describe MainWindow do
+  def ball
+    @ball = double()
+    @ball.stub(:draw) { }
+    @ball.stub(:x) { 5 }
+    @ball.stub(:y) { 5 }
+    @ball.stub(:width) { 50 }
+    @ball.stub(:height) { 50 }
+    @ball
+  end
+  describe "#initialize" do
+    it "create a new ball" do
+      Ball.should_receive(:new) { ball }
+      @x = MainWindow.new
+      @x.close
+    end
+  end
+end