fix broken Report#cache_key method, needs to be independent filter order

lib/report.rb

@@ -150,7 +150,7 @@ class Report < ActiveRecord::Base
   def cache_key
     deserialize unless @chain
     parts = [self.class.table_name.sub('_reports', '')]
-    parts.concat [filters, group_bys].map { |l| l.map(&:cache_key).sort.join(" ") }
+    parts.concat [filters.sort, group_bys].map { |l| l.map(&:cache_key).join(" ") }
     parts.join '/'
   end
 

lib/report/filter/base.rb

@@ -26,7 +26,7 @@ class Report::Filter
     end
 
     def cache_key
-      self.class.cache_key + operator.to_s + values.join(',')
+      self.class.cache_key + operator.to_s + Array(values).join(',')
     end
 
     ##
@@ -60,6 +60,12 @@ class Report::Filter
       alias :dependents :dependent
     end
 
+
+    # need this for sort
+    def <=> other
+      self.class.underscore_name <=> other.class.underscore_name
+    end
+
     def self.has_dependent?
       !dependents.empty?
     end