Fix issue where custom processors are not loaded in Rails 3

In Rails 3, Paperclip gem being loaded before the Rails object is properly configured and causing those processors not get require'd. This patch should fix that by lazy-loaded the processor.

Closes #206, #233, #247, #480, #494

lib/paperclip.rb

@@ -41,11 +41,6 @@ require 'paperclip/storage'
 require 'paperclip/callback_compatability'
 require 'paperclip/railtie'
 require 'cocaine'
-if defined?(Rails.root) && Rails.root
-  Dir.glob(File.join(File.expand_path(Rails.root), "lib", "paperclip_processors", "*.rb")).each do |processor|
-    require processor
-  end
-end
 
 # The base module that gets included in ActiveRecord::Base. See the
 # documentation for Paperclip::ClassMethods for more useful information.
@@ -106,6 +101,7 @@ module Paperclip
 
     def processor name #:nodoc:
       name = name.to_s.camelize
+      load_processor(name) unless Paperclip.const_defined?(name)
       processor = Paperclip.const_get(name)
       unless processor.ancestors.include?(Paperclip::Processor)
         raise PaperclipError.new("Processor #{name} was not found")
@@ -113,6 +109,12 @@ module Paperclip
       processor
     end
 
+    def load_processor(name)
+      if defined?(Rails.root) && Rails.root
+        require File.expand_path(Rails.root.join("lib", "paperclip_processors", "#{name.underscore}.rb"))
+      end
+    end
+
     def each_instance_with_attachment(klass, name)
       class_for(klass).all.each do |instance|
         yield(instance) if instance.send(:"#{name}?")