module is not defined

Hi Ben, I don't get this error in React Native iOS or Android, but I do in Chrome with [react-native-web](https://github.com/necolas/react-native-web). I don't know whether it's something you can publish an update to fix, or if I need to ask React Native or react-native-web to do an additional compilation step or something? 😄

```
$ npm ls immutable-tuple
/code/myapp
└─┬ aws-appsync@1.8.0
└─┬ apollo-cache-inmemory@1.3.10
└─┬ optimism@0.6.9
└── immutable-tuple@0.4.10
```

```
bundle.js:140912 Uncaught ReferenceError: module is not defined
at Module.../../../../../../../../../code/myapp/node_modules/immutable-tuple/dist/tuple.mjs (bundle.js:140912)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.../../../../../../../../../code/myapp/node_modules/optimism/lib/index.js (bundle.js:174120)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/node_modules/apollo-cache-inmemory/lib/optimism.js (bundle.js:47234)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/node_modules/apollo-cache-inmemory/lib/readFromStore.js (bundle.js:47426)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/node_modules/apollo-cache-inmemory/lib/inMemoryCache.js (bundle.js:46854)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/node_modules/apollo-cache-inmemory/lib/index.js (bundle.js:47137)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.../../../../../../../../../code/myapp/node_modules/aws-appsync/lib/client.js (bundle.js:65093)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.../../../../../../../../../code/myapp/node_modules/aws-appsync/lib/index.js (bundle.js:66186)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.../../../../../../../../../code/myapp/node_modules/aws-appsync-react/lib/rehydrated.js (bundle.js:64799)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.../../../../../../../../../code/myapp/node_modules/aws-appsync-react/lib/index.js (bundle.js:64670)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/App.js (bundle.js:824)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Module.../../../../../../../../../code/myapp/node_modules/expo/AppEntry.js (bundle.js:114414)
at __webpack_require__ (bundle.js:725)
at fn (bundle.js:102)
at Object.0 (bundle.js:281583)
at __webpack_require__ (bundle.js:725)
at bundle.js:792
at bundle.js:795
```