Before I merge this PR, I will test the change in the testnet.

Codecov Report

Merging #2580 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2580   +/-   ##
=======================================
  Coverage   93.59%   93.59%           
=======================================
  Files          45       45           
  Lines        2684     2684           
=======================================
  Hits         2512     2512           
  Misses        172      172

I tested this by updating the nginx/nginx.conf file on the testnet and then using the "Get Started" page of beta.bigchaindb.com (based on bigchaindb/site#270). It didn't work.

Then I looked at the nginx.conf template for the web proxy, and noticed this line in the 'OPTIONS' block had more stuff:

add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,app_key,app_id';

So I changed that line in the live testnet, and then the "Get Started" page worked for beta.bigchaindb.com, yay! I will make a commit to update this PR accordingly.