Allow processing some styles in foreground, some in background

Detect when only_process is set but different on has_attached_file and
process_in_background. In which case run foreground styles in normal hook,
and allow the backgrounded job to handle the styles on process_in_background
as normal.

lib/delayed_paperclip/attachment.rb

@@ -18,7 +18,7 @@ def delayed_options
 
       # Attr accessor in Paperclip
       def post_processing_with_delay
-        !delay_processing?
+        !delay_processing? || split_processing?
       end
 
       def post_processing_with_delay=(value)
@@ -34,6 +34,12 @@ def delay_processing?
           !@post_processing_with_delay
         end
       end
+
+      def split_processing?
+        @instance.class.paperclip_definitions[@name][:only_process] && 
+          @instance.class.paperclip_definitions[@name][:only_process] != 
+            @instance.class.paperclip_definitions[@name][:delayed][:only_process]
+      end
 
       def processing?
         @instance.send(:"#{@name}_processing?")