Api queries to restbase mobile-sections from iOS/Safari doesn't work when the page is a redirect, since the browser sends an `Accept-Encoding` header after the 302 but that is not allowed by the cors `Access-Control-Allow-Headers` which only reports `Accept` as a valid header to set.
As a result the browser fails to make the request.
See http://jsbin.com/cuqula/edit?js,output for broken example.
In Safari < 10 the redirect is being preflighted with an OPTIONS request with `Access-Control-Request-Headers: accept-encoding, origin, accept-language` but restbase responds with `Access-Control-Allow-Headers: accept, content-type`, which causes the request to fail (see [[ https://github.com/wikimedia/restbase/blob/master/lib/security_response_header_filter.js#L62 | wikimedia/restbase/lib/security_response_header_filter.js#L62 ]])
==Fixes==
* [x] Temporarily use a CORS proxy for Safari browsers
* Add the Safari sent headers to `Access-Control-Allow-Headers` in restbase