Added a fallback for mini_magic + ImageMagic for platforms where it is more than difficult to compile the ImageResizer

lib/danbooru_image_resizer/danbooru_image_resizer.rb

@@ -1,4 +1,8 @@
-require 'danbooru_image_resizer/danbooru_image_resizer.so'
+begin
+  require 'danbooru_image_resizer/danbooru_image_resizer.so'
+rescue LoadError
+  require 'danbooru_image_resizer/danbooru_image_resizer_fallback'
+end
 
 module Danbooru
   def resize(file_ext, read_path, write_path, output_size, output_quality)

lib/danbooru_image_resizer/danbooru_image_resizer_fallback.rb

@@ -0,0 +1,11 @@
+module Danbooru
+  def resize_image(extension, original_path, destination_path, width, height, quality)
+    require 'mini_magick'
+    image = MiniMagick::Image.open(original_path)
+    image.resize "#{width}x#{height}"
+    image.format extension
+    image.write destination_path
+  end
+
+  module_function :resize_image
+end