Package: node-browserify -> browserify
Merge pull request #184 from dcousens/ecclean

ECDSA cleanup
Merge pull request #185 from dcousens/secclean

SEC clean and bigi upgrade
Merge pull request #186 from dcousens/jsontests

JSON Test data
message: data-driven tests
message: better variable names
ecdsa: add invalid tests for verifyRaw
ecdsa: use signum() over compareTo
Merge pull request #187 from dcousens/messagefixtures

Improved message fixtures and data driven testing
ecdsa: always use signature object
Wallet: cleanup createTx control flow

Unknowingly this also revealed a subtle bug in the previous
implementation which allowed the creation of transactions even
when no UTXOs existed.  This has been amended in the tests.
Wallet: remove async interface
Wallet: use dustThreshold directly

The definition of a dust amount is pretty clear, and I feel it is less
readable when represented as isDust(amount) or !isDust(amount), by
comparison to    amount <= dustThreshold   or   amount > dustThreshold.

Also means I don't have to stray my eyes to understand the
implemention by looking up isDust does.
Wallet: remove use of hashLittleEndian
convert: remove reverseEndian
Transaction: remove TxIn/TxOut exports
Transaction: restrict TxIn input parameters

TransactionIn is only used by Transaction.prototype.addInput and the
Transaction constructor.
It is therefore safe to restrict these input parameters.
Transaction: use TxIn/TxOut consistently
Transaction: extract DEFAULT_SEQUENCE constant
Transaction: move all constants to top