Right hand story package

This introduces and A/B test with 4 different variants of right hand story cards.

# Hypothesis

Adding a large right hand story card at the bottom of articles will increase click through rate to other content across the network.

# Buckets

- Control: No card at all (25%)
- Variant A 'story-package-card' :  The card contains the first story from story curated story package (25%)
- Variant B 'most-read-card' :  The card contains the most popular article on the network (25%)
- Variant C 'latest-card' :  The card contains a random article from latest 100 articles published (25%)

# Predictions

## Chris
- 'story-package-card' :  Increase article clickthrough by 3%
- 'most-read-card' :  Increase article clickthrough by  5%
- 'latest-card' :  Increase article clickthrough by  6%

## Patrick
- 'story-package-card' :  Increase article clickthrough by 4%
- 'most-read-card' :  Increase article clickthrough by  2%
- 'latest-card' :  Increase article clickthrough by  3%


![screenshot](http://cl.ly/image/381m093M000k/Image%202013.08.20%2017%3A50%3A13.png)