* support DBWithTTL Open Interface

* add DBWithTTL_Open test

* run cargo fmt --all

* small fix to pass travis ci

* fix bug about with_ttl condition and code style

* small fix to pass travis ci

* small fix to pass travis ci

* unify the with_ttl funtion's conditon

* fix condition about with_ttl and add more tests

* little fix to pass travis ci

* little fix to pass travis ci

* fix with_ttl condition and make it more clear

* litte fix to pass travis ci