Add view type list dropdown and 'brief' view

Closes #25, #40 

* Adds new `brief` search result view
* Adds preview to brief view
* Replaces button group view types with dropdown

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![image](https://cloud.githubusercontent.com/assets/302258/3330119/6148a90c-f7cd-11e3-8788-48db2a9d0bdc.png)
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![image](https://cloud.githubusercontent.com/assets/302258/3330146/a53a55b6-f7cd-11e3-822b-ad0a47fdf72d.png)
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![image](https://cloud.githubusercontent.com/assets/302258/3330123/6cc95d26-f7cd-11e3-8436-3b18c9add8a2.png)