message: add support for passing gas price in address creation
  Summary:
  Reviewers: barath, kevin
  Subscribers: ben
diff: @@ -473,16 +473,26 @@ Wallet.prototype.createAddress = function(params, callback) {
  params = params || {};
  common.validateParams(params, [], []);
  - const chainParams = {};
  + const addressParams = {};
  +
  const chain = params.chain;
  if (!_.isUndefined(chain)) {
  if (!_.isInteger(chain)) {
  throw new Error('chain has to be an integer');
  }
  - chainParams.chain = chain;
  + addressParams.chain = chain;
  + }
  +
  + const gasPrice = params.gasPrice;
  + if (!_.isUndefined(gasPrice)) {
  + if (!_.isInteger(gasPrice)) {
  + throw new Error('gasPrice has to be an integer');
  }
  + addressParams.gasPrice = gasPrice;
  + }
  +
  const newAddress = yield this.bitgo.post(this.baseCoin.url('/wallet/' + this._wallet.id + '/address'))
  - .send(chainParams)
  + .send(addressParams)
  .result();
  // verify the new address
  