Bump version 1.6.0
Bump version 1.6.0

kenhys/redpen,kenhys/redpen,redpen-cc/redpen,recruit-tech/redpen,kenhys/redpen,kenhys/redpen,recruit-tech/redpen,redpen-cc/redpen,redpen-cc/redpen,recruit-tech/redpen,recruit-tech/redpen,redpen-cc/redpen,redpen-cc/redpen