Wed May 29 17:22:21 EDT 2013

Take a break

I'm nearing burnout.  Some things to think about later:

- add a `feedback' operator, taking a pure operator into a causal
  stream operator.

- fix delay lines so they do not need output spec, only input

  * for input delay, this inserts a siso delay

  * for siso delay: automatically insert the output wrapper.

  delays should probably be implemented after type inference has