added fold to Cause
added Step.asHalt
corrected repeatEval
fixed wye for EarlyCause\/O signature of Await
Merge branch 'append3-continue' of github.com:Spinoco/scalaz-stream into append3-step2-cause
fixed wye.disconnectL/R in AwaitBoth case
added wye.haltL/R
Merge branch 'append3-continue' of github.com:Spinoco/scalaz-stream into append3-step2-cause