change external-uid to camelcase

[sumit116]

Type of change

• Bugfix

Description of change

change external user id to camel-case from 'external_uid' to 'externalUid' since and object key cannot have underscore.

• test parameters for validating bids

{
  bidder: 'apnexus',
  params: {
   user: {externalUid:'1234567890abcdefg',age:35,gender:1,language:'EN', segments:[1,2]}
  }
}

Tested the integration with adserver using the Hello World sample page.

Other information

Jira Link: https://jira.corp.appnexus.com/browse/RAD-2553