* lib/tracer.rb: Move class overview definition and reformat


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39044 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-02-05

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39045 b2dd03c8-39d4-4d8f-98ff-823fe69b080e