Make year range validation less strict by default.
Fix CS errors.
Deprecate CacheHelper.

It has been removed from 3.0 as it was a bad idea, and better solutions
have been created outside of PHP.
throw an Exception when header is already been sent
replace whitespaces with TABs and only throw exception when Cake is in Debug mode
throw CakeException instead, putting throws tag in the comment
Fix up code formatting and structure for #3998

* Fix the various PHPCS errors.
* Make the logic less complex.
Merge pull request #4106 from cakephp/header-exception

Raise exceptions when headers have been sent
Merge pull request #4087 from dereuromark/master-validation-year

Make year range validation less strict by default.
Updating RequestHandlerComponent to accept body of HTTP Delete requests
Adding unit test for HTTP DELETE and RequestHandlerComponent::requestedWith
Fix indentation.

Refs #4108
Fix RequestHandlerComponent not unserializing JSON on DELETE requests.

Fixes #4108
`a` / `an` typo fixes fot API
Fix a fatal error occurs in combination with a scaffold error.
Merge pull request #4117 from antograssiot/master

master - `a` / `an` typo fixes for API
Merge pull request #4122 from chinpei215/master-scaffold-error-fix

Fix a fatal error occurs in combination with a scaffold error.
Update HtmlHelper.php

No need to add `null` to `$options` param as mentioned in the docs section: [Using blocks for script and CSS files](http://book.cakephp.org/2.0/en/views.html#using-blocks-for-script-and-css-files)
Merge pull request #4131 from williamn/master

Update HtmlHelper.php
Merge branch 'master' into 2.6