Remove obsolete line (was needed for Ruby 1.8.7 support)
Remove obsolete test (builtin group_by is now used)
Strengthen test with different nb of rows and columns
Return sized enumerator from Batches#find_in_batches
Return sized enumerator from Batches#find_each
Return sized enumerator from Enumerable#index_by
Merge pull request #13938 from marcandre/sized_enumerator

Sized enumerator