* lib/yaml.rb: Clarify documentation about YAML being always Psych.
  Give a tip about using Syck. See #8344.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40516 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-04-29

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40517 b2dd03c8-39d4-4d8f-98ff-823fe69b080e