1. read file as stream
2. add exclude file list opts, if the ctx.path match the exclude array, this middleware this call next
reDesign api
--folders your static folder array
--notFoundHandler function whith first arg id ctx, when not found it will be called if you set
--defer if true, middlwware will be called after the other middleware
change the condition,( defer && ctx.body || ctx.status !== 404) TO (defer && (ctx.body || ctx.status !== 404))
fix bug: when no index option and path is directory, koa-send return undefined, we thow 404 for you can handle this error;
fix bug: request method must in ['HEAD','GET']