use path.join in examples/indexes
use path.join in examples/db-create
use path.join in examples/store
use path.join in examples/get
use path.join in examples/query
use path.join in examples/keys
use path.join in examples/hierarchy
examples/hierarchy uses new store() implementation

* store() no longer returns the key only.

  * the value returned is {key: '', value: ''}
use path.join in examples/helper