message: make compatible with node 4.1.1
  Summary: We can't use let and const in the SDK yet
  Reviewers: alex, arik
  Subscribers: ben
diff: @@ -2497,8 +2497,8 @@ describe('Wallet API', function() {
  });
  describe('CPFP', function() {
  - let parentTxHash;
  - let defaultFee;
  + var parentTxHash;
  + var defaultFee;
  before(function() {
  return bitgo.unlock({ otp: '0000000' })
  @@ -2530,7 +2530,7 @@ describe('Wallet API', function() {
  });
  it('child fee capped by maxFee', function() {
  - let maxFee = defaultFee + 1000;
  + var maxFee = defaultFee + 1000;
  return bitgo.estimateFee({ numBlocks: 2, maxFee: maxFee, inputs: [ parentTxHash ], txSize: 300, cpfpAware: true })
  .then(function(result) {
  result.should.have.property('feePerKb');
  