A/B test - Gallery call to actions


Test variants of the Gallery Launch CTA against a control variant with no call to action

![cta-light](https://f.cloud.github.com/assets/518943/993745/51032516-09a0-11e3-81ba-f73e8bc28bb6.png)
![cta-dark](https://f.cloud.github.com/assets/518943/993746/529d0554-09a0-11e3-98f3-ad023147982d.png)