Fixed API task file

1. As we have vendor in AV only
2. No more vendor in AC
3. No vendor folder in AR
grab executable from rubygems
Fix order dependent test

see c48cbb02d7e6f585e31b404c0c363f0d6b586811
Back AV description in gemspec
use assert_empty in activemodel conditional validation test cases
Make AC standalone rendering work
Merge pull request #12173 from arunagw/fixes_reverted_by_revert_commit

Revert fixes
Merge pull request #12189 from rajcybage/test_assert

use assert_empty in activemodel conditional validation test cases
Don't mutate the Base settings by merge!ing the given value
Refactor handling of action normalization

Reference:
Bloody mess internals
http://gusiev.com/slides/rails_contribution/static/#40
Reset ActionView::Base.logger instead of AC::Base.logger

see: 9b0ac0bc74569db460f87ea6888b3847be0ff5be
Clean up unused associations in AR test model
change function def self.table_name to self.table_name

change def self.primary_key to self.primary_key

change def self.primary_key to self.primary_key
:scissors: [ci skip]
More unused associations in AR test models
Fixes typo in Object#try!
Be sure to restore the default I18n.locale after changed its value in a test
Update Rails 3.2.x guide link [ci skip]
Use Ruby 2.0 caller_locations instead of caller if available

* we no more have to manipulate the each caller strings by ourselves using caller_locations

* caller_locations runs slightly faster, and creates less objects than good old caller
Benchmark (loading an Engine 1000 times):
  caller: 262.89 ms
  caller_locations: 186.068 ms
Merge pull request #12193 from arunagw/revert-revert

Revert fixes