Merge pull request #81 from qiniu/develop

add warning of utf8 keys
Update CHANGELOG.md
Merge pull request #86 from qiniu/develop

Update package.json
Merge pull request #87 from qiniu/develop

Update CHANGELOG.md
Merge pull request #90 from qiniu/develop

Bug fix: check buffer
Merge pull request #96 from qiniu/develop

Release v6.1.2
Merge pull request #102 from qiniu/develop

Release 6.1.3
Merge remote-tracking branch 'origin/develop'
Merge pull request #105 from qiniu/develop

update readme
Merge pull request #108 from qiniu/develop

Release 6.1.4
Merge pull request #111 from qiniu/develop

Release 6.1.5
add insertOnly and fsizeLimit params for UploadToken
Merge pull request #118 from ahan/insertOnly_fsizeLimit_params

add insertOnly and fsizeLimit params for UploadToken
Merge pull request #120 from qiniu/develop

Release 6.1.6