upgrade qiniu sdk
add logger
remove logger
[mc] update qiniu gem version to 6.2.4
[mc] introduce domain public variable & generate download link
[mc] remove unused file
[mc] update readme
[mc] update qiniu api url
Merge pull request #1 from chaomao/master

generate download file link, support private bucket also
Merge branch 'tengcong-master'
bump version