Fix variable name in doc
Merge pull request #128 from greenmoon55/fix-variable-name-in-doc

Fix variable name in doc
add attname for download private file
Merge pull request #130 from largetalk/develop

add attname for download private file
Add delimiter to rsf.py

RESTFul API有Delimiter参数，加入到SDK中。
RESTFul API include the argument named delimiter, add it to SDK.
Merge previous commit.

Description is ame to previous commit;
Merge pull request #131 from yufeiminds/develop

Add delimiter to rsf.py
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update version [ci skip]
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Merge pull request #132 from qiniu/develop

Release 6.1.9
remove 6.x version
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