Fix transaction construction

Enable testnet by adding query param testnet=1 to the wallet url:

  file:///Users/lkang/src/bitcoinjslib-wallet/app/app.html?testnet=1

- fix transaction signing (bitcoinjs was not serializing input.seq properly)
- changed to use bitcoinjs.js (non minified with fixes.  Pull request is being submitted)
- post transaction to helloblock.io
- reduced fees to 0.0001
- added a transaction confirmation alert
- fixed a bunch of other things that broke transaction construction
@taariq @sidazhang