adding new duo and triad gallery patterns

# What's in this PR
* New 'duo' gallery pattern
![image](https://cloud.githubusercontent.com/assets/1566749/4153299/1e9649cc-3457-11e4-9bfc-8ab2eac1a63d.png)
![image](https://cloud.githubusercontent.com/assets/1566749/4153308/383c430e-3457-11e4-8559-082213a6af1e.png)

* Updated 'triad' gallery pattern with 'aligned' modifier
![image](https://cloud.githubusercontent.com/assets/1566749/4153257/9d908d38-3456-11e4-9d33-4be1fb059b9a.png)
![image](https://cloud.githubusercontent.com/assets/1566749/4153288/fe77b176-3456-11e4-8be9-498c18a10010.png)


I'd call this `Triad Gallery`.