BrowserResponseExtensions - extended range of valid HttpStatusCodes

The extension ShouldHaveRedirectedTo only allowed for '303 See Other' in the BrowserResponse Status, which is the default behaviour of the RedirectResponse class.  However there are 2 other valid statuses and if you invoked the RedirectResponse directly using either of these, the testing extension method failed, so I extended the check to include those other two statuses.