Skip check for ConstructorWithNameAsEnclosingClass when in an interface or namespace

[gooh]

PHPMD will report a violation when it finds a file like this:

namespace ACME\Foo;

interface ExtendTokenLifetime
{
    public function extendTokenLifetime($tokenString);
}

While it's easy to work around this by making the interface name a noun like TokenLifetimeExtender it feels odd having to do so when it's an interface. Interfaces should not contain constructors anyway, so assuming I defined one here feels like a bug to me. In addition, there is namespace here so the method would never not get treated as a ctor anyway.

Relates to #31