Fix of PayToSH logic in Evaluator.hs

A couple of bugs in the p2sh logic.
- Added more checking on whether the redeemScript should be evaluated
  (no empty stack, scriptPubKey had success)
- Changed the starting program state to be what is required ( need the scriptSig
  stack minus the redeemScript, and hashOps needs to be the redeemScript)
Merge pull request #71 from lornap/p2sh_bugfix

Fix of PayToSH logic in Evaluator.hs