Automatically add blog and series kickers on tag pages when no other kicker

Examples --

Before:

![screen shot 2014-11-24 at 10 10 45](https://cloud.githubusercontent.com/assets/1001642/5163355/7bf3dee0-73c2-11e4-9c26-4336603af6d9.png)

After:

![screen shot 2014-11-24 at 10 10 56](https://cloud.githubusercontent.com/assets/1001642/5163358/859bee92-73c2-11e4-8037-2509e151f842.png)

Before:

![screen shot 2014-11-24 at 10 10 02](https://cloud.githubusercontent.com/assets/1001642/5163359/8defdc52-73c2-11e4-97a0-c4a7bbe49124.png)

After:

![screen shot 2014-11-24 at 10 10 14](https://cloud.githubusercontent.com/assets/1001642/5163361/95b890e6-73c2-11e4-8840-f2e83385e8de.png)