message: fix RMG regression with classes
  Summary:
  Reviewers: kevin, bigly, tyler
  Subscribers: ben
diff: -const BaseCoin = require('../baseCoin');
  +const AbstractUtxoCoin = require('./abstractUtxoCoin');
  const prova = require('../../prova');
  const _ = require('lodash');
  -class Rmg extends BaseCoin {
  +class Rmg extends AbstractUtxoCoin {
  constructor() {
  super();
  this.network = prova.networks.rmg;
  