Added more param options to GetReviewableHITs operation

.gitignore

@@ -3,3 +3,4 @@ mturk.yml
 examples/last_hit
 pkg
 *.sw?
+.rvmrc

lib/rturk/operations/get_reviewable_hits.rb

@@ -1,22 +1,26 @@
 module RTurk
   class GetReviewableHITs < Operation
+    attr_accessor :page_size, :page_number, :hit_type_id, :status,
+                  :sort_property, :sort_direction
 
-    attr_accessor :page_size, :page_number
-
     def parse(xml)
       RTurk::GetReviewableHITsResponse.new(xml)
     end
-    
+
     def to_params
-      {
+      params = {
        'PageSize' => (page_size || 100),
        'PageNumber' => (page_number || 1)
-       }
+      }
+      params['HITTypeId'] = hit_type_id unless hit_type_id.nil?
+      params['Status'] = status unless status.nil?
+      params['SortProperty'] = sort_property unless sort_property.nil?
+      params['SortDirection'] = sort_direction unless sort_direction.nil?
+      params
     end
-
   end
+
   def self.GetReviewableHITs(*args, &blk)
     RTurk::GetReviewableHITs.create(*args, &blk)
   end
-
 end