Convert package to esm (#161)

.eslintrc.json

@@ -6,7 +6,8 @@
  "es6": false
  },
  "parserOptions": {
- "ecmaVersion": 5
+ "ecmaVersion": 6,
+ "sourceType": "module"
  },
  "rules": {
  // Possible errors

.mocharc.json

@@ -0,0 +1,3 @@
+{
+ "require": "./test/common.js"
+}

lib/sinon-chai.js

@@ -1,24 +1,6 @@
-"use strict";
 /* eslint-disable no-invalid-this */
 
-(function (sinonChai) {
- // Module systems magic dance.
-
- /* istanbul ignore else */
- if (typeof require === "function" && typeof exports === "object" && typeof module === "object") {
- // NodeJS
- module.exports = sinonChai;
- } else if (typeof define === "function" && define.amd) {
- // AMD
- define(function () {
- return sinonChai;
- });
- } else {
- // Other environment (usually <script> tag): plug in to global chai instance directly.
- /* global chai: false */
- chai.use(sinonChai);
- }
-}(function (chai, utils) {
+export default function (chai, utils) {
  var slice = Array.prototype.slice;
 
  function isSpy(putativeSpy) {
@@ -146,4 +128,4 @@
  sinonMethod("calledWithMatch", "been called with arguments matching %*", "%D");
  sinonMethod("returned", "returned %1");
  exceptionalSinonMethod("thrown", "threw", "thrown %1");
-}));
+}