Don't freeze values in pig/return
Merge pull request #86 from Netflix/unfreeze-return

Don't freeze values in pig/return
Move pigpen.io
Move pigpen.pig -> pigpen.pig.runtime
Move pigpen.exec -> pigpen.pig
Move pigpen.core to pigpen-core
Merge pull request #87 from Netflix/return-to-core

Move files back to pigpen-core
Merge branch 'sans-pig' into cascading

* sans-pig:
  Move pigpen.core to pigpen-core
  Move pigpen.exec -> pigpen.pig
  Move pigpen.pig -> pigpen.pig.runtime
  Move pigpen.io
  Don't freeze values in pig/return