FIX joins unicity

On rails-3, joins statements from different queries would not be made
properly unique, which caused sql errors.

Turned out [uniq queries method was
bogus](https://github.com/oelmekki/activerecord_any_of/blob/ee7f010382772ffa7c232f2a489cfcbcb639cbd4/lib/activerecord_any_of/alternative_builder.rb#L46)
and did not actually reduce queries array, it only worked on rails-4
because active_record was checking for duplicate itself later.
Merge pull request #23 from oelmekki/fix_join_unicity

FIX joins unicity