fix multipart content length, print exception info
merge
update README: add download url
fix client response
add onProcess
add resumable io
add upload cancelable
update utile
update resumable io
update io
update client
add Resumable demo
update
update
resumable io: fix invalid argument
update
fix bug
Merge pull request #27 from chzyer/feature/v6

fix multipart content length
Merge pull request #34 from qiniu/develop

fix multi-part length