Add FutureTimeoutSupport#timeout support

[He-Pin]

Motivation: Just like Java 's orTimeout method, which will cancel the future(if possible) and complete it with a timeout exception.

[raboof]

I like this feature idea, but do we have any particular reason to need it in 1.1.0? I think we can remove it from the milestone, it can be introduced either before or after 1.1.0.

[He-Pin]

I use something like this in an internal project, so I submitted it here to gather feedback too.

[He-Pin]

@raboof What do you think about it, I would like to finish it this weekend.

[raboof]

I like the feature idea!