OpenXBidAdapter: add support for platform ids

[rjvelicaria]

Type of change

• Bugfix
• Feature
• New bidder adapter
• 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
  additional param to support a feature in openxBidAdapter

Description of change

Users can now use either a delivery domain or a platform id provided by their OpenX representative.

Be sure to test the integration with your adserver using the Hello World sample page.

• contact email of the adapter’s maintainer
• official adapter submission

For any changes that affect user-facing APIs or example code documented on http://prebid.org, please provide:

• A link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/

Other information

[rjvelicaria]

CircleCI is posting a failed test on CMP workflow for some reason. I'm not sure how that is related to my changes.

[jsnellbaker]

@rjvelicaria Can you re-base off of master to try to clear the circleci errors? There were a few semi-recent updates we made in the test directory and a few test files to help clear these sporadic errors. So if you update your local copy, it should clear them.

[jsnellbaker]

@rjvelicaria These changes look fine. Can you put together a docs-PR (at here) to update the bidder params?

The changes you made in this repo's .md won't transition to the prebid.org site, so a separate PR for the docs repo is needed.

We should be good to merge once that's made. Thanks.

[rjvelicaria]

@jsnellbaker thanks for the help!
prebid/prebid.github.io#1033

[jsnellbaker]

Thanks for making the docs-PR. I ran the browserstack tests locally and everything passed.