* lib/csv.rb: Reject nil as data source for CSV.new, patch by @Peeja.
  [Fixes GH-580] https://github.com/ruby/ruby/pull/580


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46123 b2dd03c8-39d4-4d8f-98ff-823fe69b080e