fixed conditions with strings containing "and"/"or"

lib/liquid/condition.rb

@@ -21,6 +21,10 @@ module Liquid
     def self.operators
       @@operators
     end
+    
+    def self.operator_regexp
+      Regexp.new(@@operators.keys.sort_by(&:length).reverse.map {|k| Regexp.escape(k)}.join('|'))
+    end
 
     attr_reader :attachment
     attr_accessor :left, :operator, :right