Copy-on-write WIP
initial Java7 NIO implementation
Merge branch 'topic/copy-on-write' of github.com:scalaz/scalaz-stream into nio/async-socket
Implemented Exchange combinators.  Some treatment to Buffer
more principled `Exchange`
Defined mergeX with its algebra
Curried runStepAsyncInterruptibly in WyeActor
Implemented mergeX
Implemented topic in terms of mergeX
added Strategy as implicit parameter to wye-derived combinators
Implemented boundedQ with mergeX
added Writer1 type alias
implemented Signal in terms of mergeX, removed Ref
Removed RefActor and Ref
implemented mergeN in terms of mergeX
more specs from mergeN. cleanup + merging many streams
removed debug code and removed unused actor.messages
removed fairness check as it is nondet
added verbose info to cleanup test
Fixed mergeN so it waits for upstream to clean before terminating + enhanced spec for the cleanup case