Add top level hamburger menu to search bar

Closes #22 

Used CSS3 transform (90° rotation) for vertical hamburger menu. Added (ms-)filter to achieve the same effect in IE 6-8. 

All links are disabled for now.

![searchworks-issue22-1](https://cloud.githubusercontent.com/assets/302258/2953476/d837b174-da5a-11e3-9b16-4a969ba2a5b4.png)
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![searchworks-issue22-2](https://cloud.githubusercontent.com/assets/302258/2953478/dea4a36e-da5a-11e3-8e37-56411620ccc2.png)