prebid/Prebid.js

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Please title your pull request like this: 'Module: Change', eg 'Fraggles Bid Adapter: support fragglerock'

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Please make sure any added or changed code includes tests with greater than 80% code coverage. 

See https://github.com/prebid/Prebid.js/blob/master/CONTRIBUTING.md#testing-prebidjs for documentation on testing Prebid.js.

For any user facing change, submit a link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/
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## Type of change
<!-- Remove items that don't apply and/or select an item by changing [ ] to [x] -->
- [ ] Bugfix
- [ ] Feature
- [ ] New bidder adapter  <!--  IMPORTANT: also submit your bidder parameter documentation as noted in https://docs.prebid.org/dev-docs/bidder-adaptor.html#submitting-your-adapter -->
- [ ] Updated bidder adapter  <!--  IMPORTANT: (1) consider whether you need to upgrade your bidder parameter documentation in https://github.com/prebid/prebid.github.io/tree/master/dev-docs/bidders and (2) if you have a Prebid Server adapter, please consider whether that should be updated as well. --> 
- [ ] Code style update (formatting, local variables)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] CI related changes

- [ ] Does this change affect user-facing APIs or examples documented on http://prebid.org?
- [ ] Other

## Description of change
<!-- Describe the change proposed in this pull request -->

<!-- For new bidder adapters, please provide the following
- contact email of the adapter’s maintainer
- test parameters for validating bids:
```
{
  bidder: '<bidder name>',
  params: {
    // ...
  }
}
```

Be sure to test the integration with your adserver using the [Hello World](https://github.com/prebid/Prebid.js/blob/master/integrationExamples/gpt/hello_world.html) sample page. -->


## Other information
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