updated README.md
updated README.md

(1) added notes on KeyValueStoreSessionManager.setSticky(boolean)
(2) style issue

fengshao0907/jetty-nosql-memcached,kauppalehti/jetty-nosql-memcached-legacy,yyuu/jetty-nosql-memcached,hongzhenglin/jetty-nosql-memcached,tokuhirom/jetty-nosql-memcached