fix issue #27: lower case email address for gravatar
fix issue #27: lower case email address for gravatar

cnodejs/nodeclub,pinclub/pinclub,zaiyu-dev/club,teenworks/iLoser,pinclub/pinclub,Lottid/nodeclub,honger05/nodeclub,jayfans3/nodeclub,jayfans3/nodeclub,yorkie/nodeclub,honger05/nodeclub,Lottid/nodeclub,pinclub/pinclub,cnodejs/nodeclub,zaiyu-dev/club,zaiyu-dev/club