Increase uwsgi_buffer_size for nginx config (#716)

I was playing back a YouTube video and noticed that the playback worked
fine with using uwsgi/pywb directly but failed when using nginx. I think
a very long HTTP Link header was causing nginx to hang up. I increased
the uwsgi_buffer_size to 8k and the problem went away. Maybe this will
save someone else some time if it is increased?

https://nginx.org/en/docs/http/ngx_http_uwsgi_module.html#uwsgi_buffer_size

sample-deploy/pywb-nginx.conf

@@ -26,6 +26,7 @@ server {
         resolver 127.0.0.1;
 
         uwsgi_pass pywb:8081;
+        uwsgi_buffer_size 8k;
 
 
         include uwsgi_params;