Add provider-engine support. (#24)

* Add provider-engine support.

* Update CHANGELOG.md

CHANGELOG.md

@@ -1,7 +1,10 @@
 # Changelog
 
+## 0.3.1 (unreleased)
+ * Add support for environments using `web3-provider-engine`. ([#24](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/24))
+
 ## 0.3.0 (2019-03-19)
  * `chai` is no longer exported, and `should` is no longer automatically installed. ([#18](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/18))
- 
+
 #### How to upgrade from 0.2
 If you use Chai assertions in your project you should make sure to explicitly install it: `npm install chai`. If you need to access the `chai` instance you should now get it through `require('chai')`. If you use `should`-style assertions you should set it up manually now, by adding `require('chai/register-should')` in your tests, or e.g. in your Truffle config. Check out OpenZeppelin's upgrade commit in case it might be helpful: [`cf7375d`](https://github.com/OpenZeppelin/openzeppelin-solidity/commit/cf7375d6b873afc9f705e329db39e2ef389af9d2).

src/time.js

@@ -2,7 +2,7 @@ const { BN } = require('./setup');
 const { promisify } = require('util');
 
 function advanceBlock () {
-  return promisify(web3.currentProvider.send)({
+  return promisify(web3.currentProvider.send.bind(web3.currentProvider))({
     jsonrpc: '2.0',
     method: 'evm_mine',
   });
@@ -27,7 +27,7 @@ async function increase (duration) {
 
   if (duration.isNeg()) throw Error(`Cannot increase time by a negative amount (${duration})`);
 
-  await promisify(web3.currentProvider.send)({
+  await promisify(web3.currentProvider.send.bind(web3.currentProvider))({
     jsonrpc: '2.0',
     method: 'evm_increaseTime',
     params: [duration.toNumber()],