Some API cleanup to async
Merge remote-tracking branch 'spinoco/async-pr' into async-pr
added license file - using MIT license
Updated README w/ instructions for getting the library
Switched to h3 for readme headers
Discard AsyncRef and moved all functionality to Signal. Make `discrete` serial implementation private
Merge pull request #20 from Spinoco/async-pr

Proposed change in streams.async
added sink to signal
added async.topic
added Topic to missing def topic
added spec for topic
Changed Topic.process to val + added async.topic description
Merge branch 'refs/heads/async-pr' into topic-async-pr

Conflicts:
	src/main/scala/scalaz/stream/async.scala
Merge branch 'refs/heads/async-pr' into topic-async-pr

Conflicts:
	src/main/scala/scalaz/stream/async.scala
Merge branch 'refs/heads/topic-async-pr'