Revert "remove unnecessary object/conversions file"

This file is used at least by Active Merchant, its existence
is maybe not necessary but no big deal either.

This reverts commit ae9b3d7c.

activesupport/lib/active_support/core_ext/object.rb

 require 'active_support/core_ext/object/acts_like'
 require 'active_support/core_ext/object/blank'
-require 'active_support/core_ext/object/deep_dup'
 require 'active_support/core_ext/object/duplicable'
+require 'active_support/core_ext/object/deep_dup'
+require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/object/inclusion'
+
+require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/instance_variables'
+
 require 'active_support/core_ext/object/to_json'
 require 'active_support/core_ext/object/to_param'
 require 'active_support/core_ext/object/to_query'
-require 'active_support/core_ext/object/try'
 require 'active_support/core_ext/object/with_options'

activesupport/lib/active_support/core_ext/object/conversions.rb

+require 'active_support/core_ext/object/to_param'
+require 'active_support/core_ext/object/to_query'
+require 'active_support/core_ext/array/conversions'
+require 'active_support/core_ext/hash/conversions'

activesupport/test/core_ext/array_ext_test.rb

 require 'abstract_unit'
 require 'active_support/core_ext/array'
 require 'active_support/core_ext/big_decimal'
+require 'active_support/core_ext/object/conversions'
 
 require 'active_support/core_ext' # FIXME: pulling in all to_xml extensions
 require 'active_support/hash_with_indifferent_access'

activesupport/test/core_ext/hash_ext_test.rb

@@ -3,6 +3,7 @@
 require 'bigdecimal'
 require 'active_support/core_ext/string/access'
 require 'active_support/ordered_hash'
+require 'active_support/core_ext/object/conversions'
 require 'active_support/core_ext/object/deep_dup'
 require 'active_support/inflections'