Initial progress on TransactionBuilder
Create stubs for remainder of functions in TransactionBuilder
Implement TransactionBuilder::_getMarkerOutput
TransactionBuilder::_getMarkerOutput should return an Object

The Bitcore library does not expose the TransactionOut class in its
Transaction module. That said, transaction outputs can be represented
easily as an object with value (v) and script (s) keys. Additionally,
this format is what is expected as input to the Bitcore transaction
constructor.
Implement TransactionBuilder::_getColoredOutput
Implement TransactionBuilder::_getUncoloredOutput
Implement TransactionBuilder::_collectColoredOutputs
Cleanup and standardization in TransactionBuilder