[5.6] Added assertUri method to TestReponse

[gsingh1]

This PR is to add a simple helper to facilitate the checking of the TestResponse URI to ensure that in a test, when doing a request, the TestResponse correctly goes to an expectant URI.

Example:
$response->assertUri($uri);
instead of
$response->assertHeader('Location', $uri);

[gsingh1]

This would be great to have in the 5.5 branch too. How can I request this?
@taylorotwell
Thanks

[antonkomarev]

Maybe it was better to name it assertLocation?

[gsingh1]

Already done - see here

[antonkomarev]

Great, thanks. It will be much more clear now.