RockYou Adapter: Update for multiple ad unit support

[cameronhotchkies]

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

Description of change

Updated the RockYou Adapter to support:

• sizes coming from the mediaTypes object.
• an updated inventory zone
• multiple AdUnits

• Test parameters have been updated (including in the README)

{
    code: 'banner-div',
    mediaTypes: {
      banner: {
        sizes: [[720, 480]]
      }
    },

    bids: [{
          bidder: 'rockyou',
          params: {
            placementId: '4954'
          }
        }]
  },

  // Video (outstream)
  {
    code: 'video-outstream',
    mediaTypes: {
      video: {
        context: 'outstream',
        playerSize: [720, 480]
      }
    },
    bids: [{
      bidder: 'rockyou',
      params: {
        placementId: '4957'
      }
    }]
  }

• contact email: prebid.adapter@rockyou.com
• official adapter submission

Note: no prebid doc changes are required for this PR