scala.concurrent.Future support with typeclasses expanded greatly.

[seanparsons]

Lots more of the typeclasses, only main difference is that the object that extends FutureInstances is now called ScalazFuture, mostly because there's a method called "future" in the scalaz.concurrent package, which the original named collided with.

[larsrh]

I took the liberty to remove a bit of duplication, if you don't mind :-)

[seanparsons]

Not at all, seems sensible to me, although I'd unwrap that comment around the Copointed type as it doesn't read well now or rewrite it.