Require active_record/deselect after active_record/base is required

This will break tests because `AR::Querying.include AR::Deselect` after
`AR::Base.extend AR::Querying` doesn't add AR::Deselect's instance
methods to AR::Base.
Relax timing to require active_record/deselect.rb
Merge pull request #2 from a2ikm/relax_require_timing

Relax timing to require