Added section re: nginx message [emerg] could not build the va...

Ran into a problem with nginx "[emerg] could not build the variables_hash, you should increase either variables_hash_max_size: 512 or variables_hash_bucket_size: 64"

Based on discussion on nginx mailing list, I added this to my config and uncommented variables_hash_max_size to 1024 as this was recommended in nginx forum by developers.

Terry