ECSignature

[dcousens]

Chained on #212.

This pull request moves all the ecdsa serialize/parse functions to ECSignature, a new class interface for importing/exporting ECSignatures.

The code is straight forward enough, with the test data broken away from ecdsa fixtures, but not altered.
ECSignature.fromScriptSignature was also added to import DER signatures with a hashType byte appended on the end. It is up for debate whether this is worthwhile for now. But it will be worthwhile if we instead pass around this object and only encode it when a script signature is made.
That is, instead of createPubKeyScriptSig(DERsignatureBuffer), it is instead:

createPubKeyScriptSig = function(txSignatureInfo) {
  var signature = txSignatureInfo.signature
  var hashType = txSignatureInfo.hashType

  return Script.fromChunks([signature.toScriptSignature(hashType)])
}

This saves serialization to DER until is necessary, meaning we can allow for easier verification of signatures as an intermediary step.
This may not be the best solution, so I'm open for other ideas.

Comparison link: https://github.com/dcousens/bitcoinjs-lib/compare/txclean...ecsignature

[dcousens]

Added a jshint cleanup and upgrade to 0.9.0 of ecurve.

[coveralls]

Coverage increased (+0.01%) when pulling f429932 on dcousens:ecsignature into 4f0ae1a on bitcoinjs:master.

[coveralls]

Coverage increased (+0.01%) when pulling 1f0a54f on dcousens:ecsignature into 4f0ae1a on bitcoinjs:master.