Merge pull request qiniu#51 from qiniu/develop

Release 6.1.2

Merge pull request qiniu#45 from qiniu/develop

Release 6.1.1

Merge pull request qiniu#37 from qiniu/develop

Release v6.1.0

Merge pull request qiniu#25 from qiniu/develop

publish v6

Merge pull request qiniu#12 from why404/hotfix/sdk_docs_based_v2_4_0

hotfix / update sdk docs based on v2.4.0

imageView，imageMogr，saveAs

mkbucket, buckets

doc: small change

add x-www-form-urlencoded body for digest

docs => Docs