Improve the testing guide [ci skip]

Improve the "Testing Rails Applications" guide adding a section for
testing helpers and a little note about associations with ActiveRecord
and YAML fixtures.

Also add a link to Fixture Builder ; yet another replacement for
fixtures such as Machinist or FactoryGirl.
Remove conditional, since results are always an instance of `ActiveRecord::Result`
Remove $VERBOSE = nil from tasks.rb

Permanently setting $VERBOSE to nil causes unwanted side effects (warnings generated by app code are
silenced when triggered by a rake task but visible otherwise). silence_warnings {} would be safer to
use here since it resets $VERBOSE back to what it was when the block finishes.
Refactor `ArrayParser`

* Constantize parse token
* Remove extra param passed to `parse_data`
grab executable from rubygems

As done here d7fc97d3f90c0e30865d32ce202658f03248cacc
Update of 'The Asset Pipeline' guide for Rails 4. [ci skip]
fix order dependent test related to migration

If the order in which tests are executed is changed then test fails.
This commit ensures that all migrations are run before ensuring that
there are no pending migration.
make test order independent by resetting timezone
reset default timezone and make test order independent
make test not depend on order

`NestedThroughAssociationsTest` adds records to `member_details` table.
When test performs `@member_details[0]` then the order of record
is not guaranteed. Hence it is best to start with a clean slate by
deleting unwanted records.
Changed stylesheet load order in the stylesheet manifest generator.
Cleanup of class_name

Don't think class name is needed as by default belongs_to :select will be linked to Select class.
Merge pull request #11638 from neerajdotname/make_order_independent_association_test

make test not depend on order
Merge pull request #11637 from neerajdotname/make_test_not_depend_on_order

reset default timezone and make test order independent
Merge pull request #11635 from neerajdotname/make_test_order_independent_by_resetting_timezone

make test order independent by resetting timezone
Merge pull request #11634 from neerajdotname/fix_order_dependent_test_for_migration

fix order dependent test related to migration
Merge pull request #11641 from ankit8898/test_cleanup

Cleanup of class_name
Merge pull request #11640 from pawel2105/manifest_fix

Changed stylesheet load order in the stylesheet manifest generator.
Don't rewrite AR connection#commit_db_transaction method globally
Unneeded assertion