Version Update 2.2.0

[thrijith]

2.2.0

• Add filter rt_nginx_helper_fastcgi_purge_suffix to change purge suffix for FastCGI cache. #141 - by stayallive
• Add filter rt_nginx_helper_fastcgi_purge_url_base to change purge URL base for FastCGI cache. #141 - by stayallive
• Update our code to be in line with WordPress Coding standards in various places. #209 - by abhijitrakas
• Check and verify purging is enabled before purging cache. #168 - by jaredwsmith
• Hide Purge Cache button in admin bar when purge is disabled. #218, #219 - by mbautista, chandrapatel
• Don't add Nginx Timestamp on WordPress login page. #204, #220 - by peixotorms, chandrapatel