Fix descendants and subtree methods to work properly with scopes that…

… use joins by including the table name in the condition sql.

lib/ancestry/instance_methods.rb

@@ -171,7 +171,7 @@ def is_only_child?
 
     # Descendants
     def descendant_conditions
-      ["#{self.base_class.ancestry_column} like ? or #{self.base_class.ancestry_column} = ?", "#{child_ancestry}/%", child_ancestry]
+      ["#{self.base_class.table_name}.#{self.base_class.ancestry_column} like ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} = ?", "#{child_ancestry}/%", child_ancestry]
     end
 
     def descendants depth_options = {}
@@ -184,7 +184,7 @@ def descendant_ids depth_options = {}
 
     # Subtree
     def subtree_conditions
-      ["#{self.base_class.primary_key} = ? or #{self.base_class.ancestry_column} like ? or #{self.base_class.ancestry_column} = ?", self.id, "#{child_ancestry}/%", child_ancestry]
+      ["#{self.base_class.table_name}.#{self.base_class.primary_key} = ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} like ? or #{self.base_class.table_name}.#{self.base_class.ancestry_column} = ?", self.id, "#{child_ancestry}/%", child_ancestry]
     end
 
     def subtree depth_options = {}
@@ -229,4 +229,4 @@ def primary_key_type
       @primary_key_type ||= column_for_attribute(self.class.primary_key).type
     end
   end
-end
+end