converted imagesize plugin to lib

lib/imagesize/Manifest.txt

@@ -0,0 +1,18 @@
+Manifest.txt
+README.txt
+lib/image_size.rb
+lib/image_size/version.rb
+setup.rb
+test/test_helper.rb
+test/test_image_size.rb
+test/2-4-7.png
+test/4_1_2.gif
+test/bmp.bmp
+test/cursor.xbm
+test/detect.swf
+test/pbm.pbm
+test/pgm.pgm
+test/test.xpm
+test/tiff.tiff
+test/tokyo_tower.jpg
+test/tower_e.gif.psd