GA: custom dimensions, custom metrics, custom variables

• Before: Custom Variables -> After: Custom Dimensions & Custom Metrics
• Custom Dimensions: String
• Custom Metrics: Integer

Reference:
- How to Access Custom Dimensions in Google Analytics: http://www.lunametrics.com/blog/2013/09/10/access-custom-dimensions-google-analytics/
- Implementing Custom Variables, comparing ga.js and analytics.js: http://misterphilip.com/universal-analytics/migration/variables