replaceReved not working properly on windows

Greetings,

I just jumped from grunt to gulp because it seems to be much faster.
Unfortunately I found this bug in gulp-rev-collector:
```javascript
{ regexp: /resources\/js\/assets\.js/g, replacement: 'resources/js/assets-6889ae5e.js' }
{ regexp: /resources\/js\\assets-[0-9a-f]{8}-?\.js/g, replacement: 'resources/js/assets-6889ae5e.js' }
```
As you can see the generated regexp-replacement objects do not work the 2nd time (**js\/assets** vs **js\\\assets**)