Overload POST to support PUT/DELETE with _method query string parameter

[respect]

Overload POST to support PUT/DELETE with _method query string parameter

[wesleyvicthor]

I think that this subject is related to this one: #30

[alganet]

I've actually forgot to document this feature. It's already implemented, but somehow incomplete (It's possible to override any method, so XSS problems may appear).

$r3->methodOverriding = true;

I'm gonna work on improving security for this! Thanks =)

[augustohp]

Now the method overriding only works with POST method, the next package will be already with this fix. @ramsey Thanks again for the heads up on this issue =D

[augustohp]

Now we have tests that assure this only happens for POST, the current implementation is fixed.