passed to the constructor so that mutation isn't required after
  instantiation.

* ext/psych/lib/psych/handler.rb: add configuration object

* ext/psych/lib/psych/visitors/emitter.rb: use configuration object if
  extra configuration is present.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36458 b2dd03c8-39d4-4d8f-98ff-823fe69b080e