Remove substitute_at method from Oracle enhanced adapter
Now Arel takes care of it

Refer https://github.com/rails/rails/commit/c01b20b658c9fe4b7d54f4a227a09cb090b5763d
Merge pull request #520 from yahonda/rails42_remove_reorder_bind_params

Remove substitute_at method from Oracle enhanced adapter
Unit test updated to support `substitute_at` in Arel

Refer https://github.com/rails/arel/commit/590c784a30b13153667f8db7915998d7731e24e5
Merge pull request #522 from yahonda/rails42_substitute_at_2

Rails 4.2 Unit test updated to support `substitute_at` in Arel