Force http1.1 for nginx to enable play streaming capabilities

By default nginx proxies with http1.0 which is wrong if you want to use
chunking or any streaming capabilities of play

see http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_http_version
Merge pull request #1925 from baloo/improvements/nginx-doc

Force http1.1 for nginx to enable play streaming capabilities