fix a code broken when documenting
Merge remote-tracking branch 'astaxie/master'
Merge remote-tracking branch 'astaxie/master'
Merge remote-tracking branch 'astaxie/master'
add timeout description for file and memory cache.
add comments for config package.
gofmt code
Merge remote-tracking branch 'astaxie/master'
Merge pull request #412 from fuxiaohei/master

add comment in config package.