Bugfix: Allow empty options for truncation strategy

Fixes a regression introduced in #20 that breaks `DatabaseCleaner.clean_with(:truncation)`.

Author: clemens

lib/database_cleaner/sequel/truncation.rb

@@ -3,7 +3,7 @@
 module DatabaseCleaner
   module Sequel
     class Truncation < Base
-      def initialize(opts)
+      def initialize(opts = {})
         @only = opts[:only] || []
         @except = opts[:except] || []
         @pre_count = opts[:pre_count] || false