Remove travis hooks for notifications

Conflicts:
	.travis.yml
Don't build against ruby < 1.9.3
README

Conflicts:
	README.rdoc
Run only mysql2 test on travis
Rails config for raise on missing translations

Add a config to setup whether raise exception for missing translation or
not.

Conflicts:
	actionview/CHANGELOG.md
	actionview/lib/action_view/base.rb
	guides/source/configuring.md
	railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

Conflicts:
	actionpack/lib/action_view/base.rb
Length validation handles correctly nil. Fix #7180

When nil or empty string are not allowed, they are not valid.

Conflicts:
	activemodel/CHANGELOG.md
	activemodel/test/cases/validations/length_validation_test.rb
Merge route requirements

This was fixed upstream in rails@9b4514c
Fix issue with private kernel methods and collection associations. Closes #2508

Change CollectionProxy#method_missing to use scoped.public_send, to
avoid a problem described in issue #2508 when trying to use class
methods with names like "open", that clash with private kernel methods.
Also changed the dynamic matcher instantiator to send straight to
scoped, to avoid another roundtrip to method_missing.

Conflicts:
	activerecord/lib/active_record/associations/collection_proxy.rb
Add :conditions option to uniqueness validator

Conflicts:
	activerecord/test/cases/validations/uniqueness_validation_test.rb
Added parsing of arbitrary media type parameters.

Based on #4918.

Related to #4127.

Conflicts:
	actionpack/test/dispatch/mime_type_test.rb
no need for bang bang :bomb:
fix method visibility
Use Set#subtract and Set#merge for keeping track of used / unused keys
again, use Set#subtract
mutations can't be done without the consent of our proxy object.  This
is one benefit of choosing composition over inheritance.
rename @used to something a bit more meaningful
mutations on the underlying hash should also mutate the discard set
simplify sweep now that discard and flashes are in sync
Fix example in flash middleware
fix the Flash middleware loading the session on every request (very dangerous especially with Rack::Cache), it should only be loaded when the flash method is called