w3d.eth.getBalance() Needs to return string to match web3js

[taylorjdawson]

Users want to have a drop in replacement for web3.js, so let's give it to them!

Requirements: (For developers)

Make this w3d.eth.getBalance() return a string not the whole payload

Acceptance Criteria: (For business & QA)

w3d.eth.getBalance() returns string