ruby 2.0 does not have String#each

It was probably a bug to iterate over the characters in the string here anyway.

This manifested itself as:

undefined method each for "thread_id IS NOT NULL AND object_id IS NULL":String/Users/justin/.rbenv/versions/2.0.0-p247/gemsets/geni/bundler/gems/batch_ids-c7d30ebc3164/lib/batch_ids.rb:137:in merge_conditions