Overload put to accept a Duration

[mishaxz]

Would be nice to be able to specify an expiry time using a Duration object

[losingsleeep]

Seems that Duration class has been added since Java SE 8: Official Doc I think the project cannot depend on Java 8 because it obviously states the support of Java 6+ in the repository's README: "Supports Java 6+ though the documentation uses lambdas for simplicity."