Merge pull request #292 from ideawu/dev

merge dev, 1.6.8.7
Merge pull request #294 from ideawu/dev

add ttl command
Update SSDB.js

Don't put property of array into command
Merge pull request #296 from ahkimkoo/patch-1

Update SSDB.js
Merge pull request #297 from ideawu/master

merge master