* lib/delegate.rb: [DOC] Document raise in Delegator class
  Patch by @lucasmazza. [Fixes GH-621]
  https://github.com/ruby/ruby/pull/621


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46264 b2dd03c8-39d4-4d8f-98ff-823fe69b080e