Site: configure Jekyll to use Etc/GMT+5 timezone for consistent page URLs

Jekyll seems to use client's time zone by default, and it causes
separate-project.html to be rendered as 2016/03/03 or 2016/03/04
depending on the build timezone.

Hopefully Etc/GMT+5 sorts that out
diff --git a/site/_config.yml b/site/_config.yml
index 1deecde..1fc3bfa 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -21,6 +21,9 @@
 destination: target/avatica
 exclude: [README.md,Gemfile*,add-avatica-go-docs.sh,docker-compose.yml,target]
 keep_files: [".git", ".svn", "apidocs", "testapidocs"]
+# This ensures 2016-03-03-separate-project.md is rendered 2016-03-03
+# no matter what the client time zone is
+timezone: Etc/GMT+5
 
 collections:
   docs: