Start IntegrationTestCase.

Not much here, but getting something down is a start.
Start to flesh out IntegrationTestCase.

Start adding an integration test for IntegrationTestCase - how meta.
Remove dead code.

This code is no longer needed, it can be removed safely.
Very crude dispatch cycle is working now.

The code is pretty simple right now as it doesn't attempt any fancy
footwork around mocks or giving you ways to only get the just the view
without the layout. It is also not possible to get the view variables
just yet.

I've also added a stub response to smooth over any issues where someone
might try and send a response by accident or on purpose :)
Fix header manipulation.

Convert headers from the format humans expect to the format PHP uses
internally.
Implement assertResponseXX methods.

Add positive tests for assertResponseXX methods, the negative tests seem
less useful right now.
Add assertRedirect()
Fix typos and expand docs.
Add assertResponseContains() to IntegrationTestCase.
Add more assertion methods.
Add exception handling to IntegrationTestCase.

Rendering exceptions is part of the 'integration' aspect of integration
testing.
Remove offset from cloned queries used in subquery loads.

Having an offset in a subquery causes SQL errors in MySQL. Also
include a test to ensure HAVING is not an issue.

Fixes #4465
Fix typos.
Remove outdated information
SecurityComponent::requireSecure() should accept empty argument
Remove problematic test.

This test will always pass in MySQL/SQLite but will always fail in
Postgres/SQLserver. Since it provides no real value there is no point in
keeping it.
Merge pull request #4482 from dereuromark/3.0-phpunit

Remove outdated information
Merge pull request #4483 from spiliot/3.0-requiresecure-empty

SecurityComponent::requireSecure() should accept no argument
Merge pull request #4473 from cakephp/issue-4465

Remove offset from cloned queries used in subquery loads.
Add query->clear().

I found a few duplicated blocks of code related to clearing query state
when subqueries are created. Having a function will help prevent code
getting out of sync in the future.