Merge pull request #459 from ideawu/master

sync with master
Add qtrim_front, qtrim_back commands
Add export, import commands in ssdb-cli
ssdb-cli performance improved
fix install script
fix ssdb-cli bug
update string.h str_unescape
update ssdb-cli
Merge pull request #462 from ideawu/dev

merge dev:

Add qtrim_front, qtrim_back commands
ssdb-cli performance improved
Add export, import commands in ssdb-cli