Fix sinonjs/sinon#1143: Only overwrite globals when running in IE

[mroderick]

This is a PR for master, it is a solution for sinonjs/sinon#1143

The PR fixes compatibility with React Native and quite possibly other libraries.

To verify bug

1. Run test in https://github.com/mroderick/sinon-issue-1143
2. Observe that an error occurs

TypeError: Date is not a constructor

  at new MessageQueue (node_modules/react-native/Libraries/Utilities/MessageQueue.js:62:26)
  at Object.<anonymous> (node_modules/react-native/Libraries/BatchedBridge/BatchedBridge.js:17:19)
  at Object.<anonymous> (node_modules/react-native/Libraries/Utilities/RCTLog.js:14:19)
  at setUpConsole (node_modules/react-native/Libraries/JavaScriptAppEngine/Initialization/InitializeJavaScriptAppEngine.js:54:1)

To verify solution

1. Check out this PR, switch into that folder
2. npm link
3. Switch back to your sinon-issue-1143 folder that you just used above
4. cd node_modules/sinon/
5. npm link lolex
6. cd -
7. npm test
8. Observe that test test passes

[mroderick]

Thanks