Remove Allows header check

It is not clear that we should be checking for the ALLOW header when testing. This was discussed in [27](#27). Allow is part of CORS and we are likely using it wrongly. The proposed way of dealing with this is to remove it until we know what we want to achieve with it.

runtest

@@ -375,9 +375,7 @@ class Noark5Tester (n5core.endpoint.Endpoint):
             urlseen[url] = 1
             try:
                 (content, res) = self.json_get(url)
-                allow = res.getheader('Allow')
                 self.success("GET %s worked with code %d"  % (url, res.code))
-                self.verify(allow is not None, "GET header should include Allow for %s" % url)
                 ctype = res.getheader('Content-Type')
 
                 if not ctype: