📢 Optimized the SteemDB.io

The steemdb.io service has been unstable for a while. I have time today to look into the issues.

I saw many http 499 errors on nginx log and many errors on website log.

Find that the php-fpm and nginx configuration were not fit current situation.

So I changed some parameters of nginx and php-fpm.

https://github.com/steemit/steemdb/commit/f2074b46c4085626835f9ca2b4f863bcdac0a18a

The site seems work fine after these configuration were set.

I also do some other optimizations.