Allow JS requests from other origins

Add "add_header 'Access-Control-Allow-Origin' '*';" option to the nginx config to allow html/js instances of the what's fresh mobile UI access to the API via javascript. Avoids CORS issues.
It could even be staff.osuosl.org rather than '*' because I think the instance in my staff web space is the only such instance, and I don't forsee others being needed outside of another developer also using their staff web space to test.