Increased timeout back to 20s. Added relevant docstring

config.ru

+# It is possible that the rack time out here is set to a different value than
+# on the edx-platform django_comment_client timeout. An attempt was made to
+# move these two values closer together (5s django_client_comment, 6s 
+# cs_comments_service from 20). This resulted in more reported timeout errors
+# on the cs_comments_service side which better reflected the timeout errors the
+# django_comment_client. On the downside, the shorter timeout lead to less time 
+# for processing longer queries in the background. The timeout has been set back
+# to 20s. Until these slow queries that benefit from being cached in the 
+# background are resolved, reducing the timeout is not suggested. 
+# More conversation at https://github.com/edx/cs_comments_service/pull/146
+# -Nov 18th, 2015
+
 require "rack-timeout"
 use Rack::Timeout           # Call as early as possible so rack-timeout runs before other middleware.
-Rack::Timeout.timeout = 6
+Rack::Timeout.timeout = 20 
 
 require './app'
 run Sinatra::Application
-