Merge branch 'new-contracts'

* new-contracts: (29 commits)
  Fix a typo
  Fix a typo in comment
  Rename shouldCheckTransfer to shouldThrowOnInsufficientBalanceOrAllowance
  Simplify BigNumber hack
  use yarn on CI
  Upgrade to a new node version
  Make CONTRACTS_COMMIT_HASH a string
  Use never testrpc snapshot
  Migrate the rest of the artifacts
  Change arguments order at isRoundingError
  Migrate events
  Migrate constructor arguments
  Migrate fillOrKillOrder
  Migrate ZRX_TOKEN_AMOUNT
  Migrate getUnavailableTakerTokenAmount
  Migrate PROXY_CONTRACT
  Migrate batchFillOrKillOrders
  Migrate batchFillOrders
  Migrate fillOrder
  Migrate fillOrdersUpTo and remove min
  ...

1 files changed, 2 insertions, 5 deletions

diff --git a/src/utils/event_utils.ts b/src/utils/event_utils.ts
index 07418cbc4..e8f30e1a8 100644
--- a/src/utils/event_utils.ts
+++ b/src/utils/event_utils.ts
@@ -1,5 +1,4 @@
 import * as _ from 'lodash';
-import * as Web3 from 'web3';
 import {EventCallback, ContractEventArg, ContractEvent, ContractEventObj, ContractEventEmitter} from '../types';
 import * as BigNumber from 'bignumber.js';
 import promisify = require('es6-promisify');
@@ -29,10 +28,8 @@ export const eventUtils = {
                 const wrapIfBigNumber = (value: ContractEventArg): ContractEventArg => {
                     // HACK: The old version of BigNumber used by Web3@0.19.0 does not support the `isBigNumber`
                     // and checking for a BigNumber instance using `instanceof` does not work either. We therefore
-                    // compare the constructor functions of the possible BigNumber instance and the BigNumber used by
-                    // Web3.
-                    const web3BigNumber = (Web3.prototype as any).BigNumber;
-                    const isWeb3BigNumber = web3BigNumber.toString() === value.constructor.toString();
+                    // check if the value constructor is a bignumber constructor.
+                    const isWeb3BigNumber = _.startsWith(value.constructor.toString(), 'function BigNumber(');
                     return isWeb3BigNumber ?  new BigNumber(value) : value;
                 };
                 event.args = _.mapValues(event.args, wrapIfBigNumber);