experimenting with parallel script evaluation.
eval_script: OP_ELSE Through the Looking Glass.
OP_ELSE High Weirdness... and more.

pprint_script: OP_ELSE.
dump: do a better job of print stacks.
verify_sig: cater to SIGHASH_SINGLE bug.
get_ecdsa_hash -> get_tx_for_hash
get_tx_for_hash: SIGHASH_SINGLE.
check_one_sig: fail gently on empty sig.
verifying_machine: proper exit conditions.
eval_script:
  OP_ELSE.
  push CHECKSIG result.
do_equal: simplered.
do_return: implemented.
do_verify: pop-on-true.
pinsn: OP_ELSE, use W rather than print.
TX.verify: logic moved to m.eval_script.
API change for KEY.verify:
  hopefully someday we can forget about the SIGHASH_SINGLE bug and re-enable crypto++.
collect failures into a file.  use argparse.
verify_wrapper: format output for test_txns.py + commented tx.name.
Merge branch 'master' of github.com:samrushing/caesure