Use the term "sorted" instead "ordered" when mentioning SortSet.

* lib/set.rb: [DOC] Use the term "sorted" instead "ordered" when
  mentioning SortSet.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42263 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* lib/set.rb: [DOC] Fix example result.  Hash is now ordered.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42264 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* lib/set.rb: [DOC] Add a couple of notes on Hash as storage.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42265 b2dd03c8-39d4-4d8f-98ff-823fe69b080e