Get Transaction test cases running

I removed the skip over the tx_valid.json file and made some tweaks to get most of the test cases passing.  There are still two test cases that fail, as pointed out by the TODO comment I added above them. Oddly, running the test suite reports 3 failing test cases, but if I delete the two marked with the TODO there are 0 reported failures. So, there may be some kind of interaction with these test cases and the others. More investigation is needed.

I updated the two test cases that were testing transaction `23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63` with the input script I found on blockchain.info https://blockchain.info/tx/23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63. A quick search found one other person who was using this same script (https://github.com/lian/bitcoin-ruby/blob/master/spec/bitcoin/fixtures/23b397edccd3740a74adb603c9756370fafcde9bcc4483eb271ecad09a94dd63.json) and the test passes now, so I'm not sure why the old script was being used.

All of the other changes are simply re-formatting decimal numbers as hex (i.e. `1` => `0x01`).

Furthermore, I added some code in the test fixture itself to verify each of the inputs.

Test Plan:
`mocha -R spec test/test.Transaction.js`
Reverting modifications of testdata
Work in progress. I have a problem with the verifyInput() callback calling itself whenever the test assertions throw an exception. I looked at the step and async libraries that are already installed via package.json, but I don't think either of these provide the functionality I need.
Refactor parsing test data into function, add iteration over invalid transaction tests
Fix merge problem
Update invalid transaction test case
Mark failing tests with skip()
Remove console.log() statements
remove console.log
some Transaction tests fixed (canonical signatures)
refactor and fixes for Transaction, ScriptInterpreter, and Key
fix test code for Transaction. Test skipped because they still fail
fix util problem
Merge pull request #170 from MattFaus/fix_transaction_tests2

Hook up testdata/tx_valid.json and tx_invalid.json test cases