Unset association when existing record is destroyed.

To avoid foreign key errors (and invalid data) in the database, when a belongs_to association is destroyed, it should also be nil'd out on the parent object.
use template0 option for creating activerecord test databases in postgres build_database task
Raise generic ParseError exception when ActionDispatch::ParamsParser fails parsing request params.
Fix ActionDispatch::ParamsParser::ParseError message for XML and JSON parsers.
Make ActionDispatch::ParamsParser::ParseError#original_exception return the original exception.
fix punctuation in Getting Started prologue [ci skip]
More concise flash output
Merge pull request #113 from lifo/gr-flash-output

Ran the generators and had no further changes. Merging.
Nice and easy delegation to the class
Fix typo [ci skip]
Update action_controller_overview.textile to ruby 1.9 syntax [ci skip]
update some AS code examples to 1.9 hash syntax [ci skip]
update AS/core_ext docs [ci skip]
fix AS/core_ext examples [ci skip]
Implement :null_session CSRF protection method

It's further work on CSRF after 245941101b1ea00a9b1af613c20b0ee994a43946.

The :null_session CSRF protection method provide an empty session during
request processing but doesn't reset it completely (as :reset_session
does).
Merge pull request #6348 from LTe/no_global_depreactations

Allow ActiveSupport::Deprecation features to be used by rails applications and library authors
refactor store_accessor
Merge pull request #7524 from al2o3cr/store_boolean

Add boolean type conversion for AR::Store
Copy-edit deprecation relared documentation [ci skip]
Remove redundant 'the'.